MousePosition Offset

Ok, so I have this code and its suppose to move a trigger to the position of where you click and it kind of does that. It moves the trigger alright and I fixed the problem with the Y but I don't know how to fix the x and z because there just completely off from where its suppose to be.

 Vector3 MousePos;
 public int TapDamage = 10;
 Vector3 StartPos;
 Vector3 Temp;


 private void Start()
 {
     StartPos = gameObject.transform.position;
 }

 void MovingClickBox()
 {
     if (Input.GetMouseButtonDown(0) == true)
     {
         MousePos = Input.mousePosition;

         gameObject.transform.position = MousePos;
         Temp = gameObject.transform.position;
         Temp.y = 1;
         gameObject.transform.position = Temp;
      
     }

 }
 private void FixedUpdate()
 {
     MovingClickBox();

 }

}