I cant figure out how to change my simple Movement controls to touch, can anyone help?

Hello, I need some help on how to change this movement script of mine to touch controls if possible. I'm extremely new to this and have been looking all over for how to do this but it just doesn't make sense to me. If you could accomplish touch controls without changing much that would be awesome because the script is put onto the player and has restrictions that only work the way I currently have it setup. Here is what I have:

 using UnityEngine;
 using System.Collections;
 
 public class Movement : MonoBehaviour {
     
     float lerpTime;
     float currentlerpTime;
     float perc = 1;
     
     Vector3 startPos;
     Vector3 endPos;
 
     public float minX = 0;
     public float maxX = 2;
     public float minZ = 0;
     public float maxZ = 1;
 
 
     bool firstInput;
     public bool justJump;
 
 
 
     void Update () 
     {
 
 
         if (Input.GetButtonDown ("up") || Input.GetButtonDown ("down") || Input.GetButtonDown ("left") || Input.GetButtonDown ("right")) 
         {
             if(perc == 1)
             {
                 lerpTime = 1;
                 currentlerpTime = 0;
                 firstInput = true;
                 justJump = true;
             }
         }
         startPos = gameObject.transform.position;
         if(Input.GetButtonDown("right") && gameObject.transform.position == endPos && transform.position.x < maxX)
         {
             endPos = new Vector3(transform.position.x + 1,transform.position.y,transform.position.z);
         }
         if(Input.GetButtonDown("left") && gameObject.transform.position == endPos && transform.position.x > minX)
         {
             endPos = new Vector3(transform.position.x - 1,transform.position.y,transform.position.z);
         }
         if(Input.GetButtonDown("up") && gameObject.transform.position == endPos && transform.position.z < maxZ)
         {
             endPos = new Vector3(transform.position.x,transform.position.y,transform.position.z + 1);
         }
         if(Input.GetButtonDown("down") && gameObject.transform.position == endPos && transform.position.z > minZ)
         {
             endPos = new Vector3(transform.position.x,transform.position.y,transform.position.z - 1);
         }
         if (firstInput == true) {
             currentlerpTime += Time.deltaTime * 5;
             perc = currentlerpTime / lerpTime;
             gameObject.transform.position = Vector3.Lerp (startPos, endPos, perc);
             if (perc > 0.8F) {
                 perc = 1;
             }
             if (Mathf.Round (perc) == 1) {
                 justJump = false;
             }
         }
         
     }
 }