2D Building Script Help Needed

C# I am using 3d Cubes in this 2d sandbox game because 2d Quads didn't work.

 using System.Collections;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class Inventory : MonoBehaviour {
     public Text InventoryText, SelectionText;
     int[] counts = new int[7];
     int selectedTile;
     string[] names = new string[] { "Dirt", "Turf", "Stone", "Iron", "Ramp", "Diamond", "Solid Fuel" };
     public GameObject[] tiles = new GameObject[7];
 
     void Update()
     {
         InventoryText.text = "Dirt: " + counts[0] + "Turf: " + counts[1] + "Stone: " + counts[2] + "Iron: " + counts[3] + "Ramps: " + counts[4] + "Diamond: " + counts[5] + "Solid Fuel: " + counts[6];
         if (selectedTile < 0)
         {
             selectedTile = counts.Length - 1;
         }
         if (selectedTile > counts.Length - 1)
         {
             selectedTile = 0;
         }
         if (Input.GetKeyDown(KeyCode.UpArrow))
         {
             selectedTile++;
         }
         if (Input.GetKeyDown(KeyCode.DownArrow))
         {
             selectedTile--;
         }
         SelectionText.text = names[selectedTile];
         if (Input.GetMouseButtonDown(1)){
 
             if (counts[selectedTile] > 0)
             {
                 Vector3 mousepos = Camera.main.ScreenToWorldPoint(Input.mousePosition);
                 Vector3 placepos = new Vector3(Mathf.Round(mousepos.x), Mathf.Round(mousepos.y), 0f);
 
                 if (Physics2D.OverlapCircleAll(placepos, 0.25f).Length == 0)
                 {
                     GameObject newTile = Instantiate(tiles[selectedTile], placepos, Quaternion.identity) as GameObject;
                     counts[selectedTile]--;
                 }
             }
         }
     }
     public void Add(int tileType, int count){
         counts[tileType] += count;
     }
 }
 

Thanks :)