grid-based block placement system with touch input

I created a grid-based block placement system with mouse input like this video: https://youtu.be/0WZUgUtBxcg?t=1982

At the moment I can only place blocks with a click of the mouse at the point I am looking at. Now I want to place the blocks with touch input on mobile devices. I am new to Unity so can someone give me hints or even better adjust the code right away? Here is the code:

 `using System.Collections;  
 using System.Collections.Generic;  
 using UnityEngine;  
 public class BuildingSystem : MonoBehaviour  
 
 {
 
     [SerializeField]
     private Camera playerCamera;
 
     private bool buildModeOn = true;
     private bool canBuild = true;
 
     private BlockSystem bSys;
 
     [SerializeField]
     private LayerMask buildableSurfacesLayer;
 
     private Vector3 buildPos;
 
     private GameObject currentTemplateBlock;
 
     [SerializeField]
     private GameObject blockTemplatePrefab;
     [SerializeField]
     private GameObject blockPrefab;
 
     [SerializeField]
     private Material templateMaterial;
 
     private int blockSelectCounter = 0;
 
     private void Start()
     {
         bSys = GetComponent<BlockSystem>();
     }
 
     private void Update()
     {
         if (Input.GetKeyDown("e"))
         {
             buildModeOn = !buildModeOn;
 
             if (buildModeOn)
             {
                 Cursor.lockState = CursorLockMode.Locked;
             }
             else
             {
                 Cursor.lockState = CursorLockMode.None;
             }
         }
 
         if (Input.GetKeyDown("r"))
         {
             blockSelectCounter++;
             if (blockSelectCounter >= bSys.allBlocks.Count) blockSelectCounter = 0;
         }
 
         if (buildModeOn)
         {
             RaycastHit buildPosHit;
 
             if (Physics.Raycast(playerCamera.ScreenPointToRay(new Vector3(Screen.width / 2, Screen.height / 2, 0)), out buildPosHit, 10, buildableSurfacesLayer))
             {
                 Vector3 point = buildPosHit.point;
                 buildPos = new Vector3(Mathf.Round(point.x), Mathf.Round(point.y), Mathf.Round(point.z));
                 canBuild = true;
             }
             else
             {
                 Destroy(currentTemplateBlock.gameObject);
                 canBuild = false;
             }
         }
 
         if (!buildModeOn && currentTemplateBlock != null)
         {
             Destroy(currentTemplateBlock.gameObject);
             canBuild = false;
         }
 
         if (canBuild && currentTemplateBlock == null)
         {
             currentTemplateBlock = Instantiate(blockTemplatePrefab, buildPos, Quaternion.identity);
             currentTemplateBlock.GetComponent<MeshRenderer>().material = templateMaterial;
         }
 
         if (canBuild && currentTemplateBlock != null)
         {
             currentTemplateBlock.transform.position = buildPos;
 
             if (Input.GetMouseButtonDown(0))
             {
                 PlaceBlock();
             }
         }
     }
 
     private void PlaceBlock()
     {
         GameObject newBlock = Instantiate(blockPrefab, buildPos, Quaternion.identity);
         Block tempBlock = bSys.allBlocks[blockSelectCounter];
         newBlock.name = tempBlock.blockName + "-Block";
         newBlock.GetComponent<MeshRenderer>().material = tempBlock.blockMaterial;
     }
 }`