How to position input field characters inside background boxes

I wrote a code for you try to see if it is right for you, if you like it and you want to optimize it I can continue to help you. It is necessary: that you add this code to your panel and that all the boxes are InputFields, in charactersID and LV set the value corresponding to your fields

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class AddLevel : MonoBehaviour
 {
     [SerializeField] private InputField[] charactersID;                     //This array contains all "InputField-Text" GameObject in Hierarchy    (Canvas->UI)
     [SerializeField] string[] stringsID;                                    //This one contains the input values we insert in each inputfield that we will add up 
 
     [SerializeField] private InputField[] charactersLV;                     
     [SerializeField] string[] stringsLV;                                 
 
     [Space(20)] [SerializeField] public string ID;                         
     [Space(20)] [SerializeField] public string LEVEL;                      
 
     private int indexID = 0;                                                //This is a reference for the arrays
     private int indexLV = 0;
     private string tempID;                                                  //This is a temporary variable that will contains ours adds of strings. It will be the integer ID
     private string tempLV;
     private bool runOnce;                                                   //This variable is used for run a method once time and not update every frame
 
     
     
 
     private void Awake()
     {
         stringsID = new string[charactersID.Length];                        //Initializing of the strings for each value
         stringsLV = new string[charactersLV.Length];
         runOnce = false;                                                    
     }
 
     private void Update()
     {
         //Update function can be removed if you want to load script from other event
         Application();
     }
 
 
     #region StartProgram
     public void Application()
     {
 
         //START THE FIRST PART WHERE WE INSERT THE ID VALUE
         //Check if ID area isn't already used or completed
         if (indexID < charactersID.Length)
         {
             if(indexID == 0)
             {
                 //Start with first box selected (if-index==0)
                 charactersID[indexID].Select();
             }
 
             //Updated methods
             InsertValueID();
             ReadyToWriteID();
         }
 
         //Level ready check
         else
         {
             if (indexLV == 0)
             {
                 charactersLV[indexLV].Select();               
             }
             InsertValueLevel();
             ReadyToWriteLevel();
         }
 
 
     }
 
     #endregion
 
     #region ID
     private void InsertValueID()
     {
 
         runOnce = true;
         if (indexID < charactersID.Length)
             charactersID[indexID].onValueChanged.AddListener(delegate { NextValueID(); });  //onValueChanged can be found in InputField (addListener used for runtime next method)
 
     
     }
 
     private void NextValueID() //Selects the next input field once you leave one
     {
 
         if (runOnce)
         {
             //Here inserted the value we are going to add it to the array String
             ReplaceAtID(stringsID, indexID);
 
             //check if there are still fields and add index++
             if (indexID < stringsID.Length)
                 indexID++;            
 
             //select the next inputfield
             if (indexID < charactersID.Length)
             {
                 charactersID[indexID].Select();
             }
         }
 
         runOnce = false;
     }
 
     private void ReplaceAtID(string[] strings, int index)
     {
         //We insert the input value with the position in the string point
         strings[index] = charactersID[index].text;  
         
     }
 
     private void ReadyToWriteID()
     {
         
         if (indexID == charactersID.Length - 1)
         {
             //At the end we can call the method to write the id
             charactersID[indexID].onValueChanged.AddListener(delegate { GetID(); });
             
         }
     }
 
     private string GetID()
     {
         for (int i = 0; i < stringsID.Length; i++)
         {
 
             //sum of each index in array
             tempID += stringsID[i];
             Debug.Log("Writing ID" + tempID);
 
             if (i <= stringsID.Length)
             {
                 ID = tempID;
                 Debug.Log("GET ID" + ID);
             }
         }
 
         tempID = "";
         return ID;
         
 
     }
 
     #endregion
 
     //SAME SPEECH
     #region LEVEL
 
     private void InsertValueLevel()
     {
 
         runOnce = true;
         if (indexLV < charactersLV.Length)
             charactersLV[indexLV].onValueChanged.AddListener(delegate { NextValueLevel(); });
 
 
     }
 
     private void NextValueLevel()
     {
 
         if (runOnce)
         {
             ReplaceAtLevel(stringsLV, indexLV);
 
             if (indexLV < stringsLV.Length)
                 indexLV++;
 
             if (indexLV < charactersLV.Length)
             {
                 charactersLV[indexLV].Select();
             }
         }
 
         runOnce = false;
     }
 
     private void ReplaceAtLevel(string[] stringsLV, int indexLV)
     {
 
         stringsLV[indexLV] = charactersLV[indexLV].text;
 
     }
 
     private void ReadyToWriteLevel()
     {
         if (indexLV == charactersLV.Length - 1)
         {
 
             charactersLV[indexLV].onValueChanged.AddListener(delegate { GetLevel(); });
 
         }
     }
 
     private string GetLevel()
     {
         for (int i = 0; i < stringsLV.Length; i++)
         {
 
             tempLV += stringsLV[i];
             Debug.Log("Writing Level: " + tempLV);
 
             if (i <= stringsLV.Length)
             {
                 LEVEL = tempLV;
                 Debug.Log("Get Level: " + LEVEL);
             }
         }
 
         tempLV = "";
         return LEVEL;
 
 
     }
 
     #endregion
 }