[Unity 2D]Grid Based Character Movement Issues with Vector3D.movetowards

So I am new to C# and Unity...I am trying to create a script that allows the object to move in a grid-fashion (fixed unit displacement of the object per direction input). My current code represents a free movement style...

So here is the code:

 using UnityEngine;
 using System.Collections;
 
 public class PlayerMovement : MonoBehaviour
 {
     public LayerMask BlockingLayer;
     private BoxCollider2D Box_Collider;
     private Rigidbody2D RB2D;
     RaycastHit2D hit;
    
     Vector3 pos;                                // For movement
     float speed = 2.0f;                         // Speed of movement
 
     void Start()
     {
         Box_Collider = GetComponent<BoxCollider2D>();
         RB2D = GetComponent<Rigidbody2D>();
         pos = transform.position;          // Take the initial position
         print(pos);
         
     }
 
     void FixedUpdate()
     {
         DirectionCheck(pos);
         pos = transform.position; 
     }
     void DirectionCheck(Vector3 pos)
     {
         if (Input.GetKey(KeyCode.LeftArrow) && transform.position == pos)
         {
             pos += Vector3.left; // Left
             print(pos);
             CanMove(pos,out hit);
             return ;
         }
              if (Input.GetKey(KeyCode.RightArrow) && transform.position == pos)
             {
             pos += Vector3.right; // Right 
             print(pos);
             CanMove(pos, out hit);
             return ;
         }
                  if (Input.GetKey(KeyCode.UpArrow) && transform.position == pos)
                 {
                     pos += Vector3.up; // Up    
             print(pos);
             CanMove(pos, out hit);
             return;
         }
                     if (Input.GetKey(KeyCode.DownArrow) && transform.position == pos)
                     {
                         pos += Vector3.down; // Down 
            print(pos);
             CanMove(pos, out hit);
             return;
         }
 
         return;
     }
     bool CanMove(Vector3 pos,out RaycastHit2D hit) {
         //print(pos);
         Box_Collider.enabled = false;      
         hit = Physics2D.Linecast(transform.position, pos, BlockingLayer);
         Box_Collider.enabled = true;
         MovePlayer(pos,hit);
         return hit;
     }
     private RaycastHit2D  MovePlayer(Vector3 pos,RaycastHit2D hit)
     {
         if (!hit)
         {
             transform.position = Vector3.MoveTowards(RB2D.position, pos, Time.deltaTime * speed);// Move there
             RB2D.MovePosition(transform.position);
            // print(pos);
             return hit;
        
         }
         else{
             //print(pos);
            
            return hit;
         }
     }
    
 }

I use getkey() to get the input directions to move which is done by : "vector3.right/down/left/up"

I have used Physics2D.Linecast to detect collision at the destination and return true/false with "hit"... then Vector3.movetowards does the moving...but the code ended up not moving in grids....

any directions to how to implement a grid-based movement?