Transform does not move GameObject

Hi, I'm pretty new to c# and unity so please bare with me. I want to transform.position a Gameobject on a grid by using collider.bounds.center as a vector 3 reference. I am trying to do this through a tilescript which equals one tile in an array. When I instantiate the GameObject/PlayerPrefab I am able to clone the Gameobject onto each tile (which is what I want to do with the transform.position). However when I try to transform.position the GameObject nothing works.

 public class TileScript : MonoBehaviour {
     
     public Vector3 tileCenter;
     public GameObject PlayerPrefab;
     public PlayerScript Select;
     public float x,y,z;
 
     // Use this for initialization
     void Start () {
         //tileCenter = new Vector3 (x, 3, z);
 
         x = this.transform.collider.bounds.center.x;
         y = this.transform.collider.bounds.center.y;
         z = this.transform.collider.bounds.center.z;
 
         }        
     void Update () {
         
     }
 
     
     void OnMouseEnter() {
         gameObject.transform.renderer.material.color = Color.blue;
     }
 
     
     void OnMouseExit() {
         transform.renderer.material.color = Color.white;
         }
 
     public void OnMouseDown()
         {
         PlayerPrefab.transform.position =  new Vector3 (x, 3, z);
         //if (Select.selected == true) 
             //var Move = Instantiate(PlayerPrefab, new Vector3 (x,0,z), Quaternion.AngleAxis (0,Vector3.right));        
             //tileCenter = newPos;
             //print (x);
     }
 }
         

I have tried multiple variations of transform.position, none seem to work. Any help would be appreciated, thanks.