Spawn random amount apart of each other

I have a script, which spawns a random amount of gameobjects, on a random place on the screen. Now my problem is that, the amount of gameobjects are spawned in the same place so lets say It spawns an amount of five, then all five gameobjects, spawn on top of each other, where they are supposed to spread instead. How can I fix this?

This is my script so far.

 var Mines : Transform;
 
 private var Timer : float;
 
 function Awake () {
     Timer = Time.time + 4;
 }
 
 function Update () {
     
     var randNum = Random.Range(0, 5); // this will return a number between 0 and 9 
      var screenPosition : Vector3 = Camera.main.ScreenToWorldPoint(new Vector3(Random.Range(0,Screen.width), Random.Range(0,Screen.height), Camera.main.farClipPlane/2));
  
      if (Timer < Time.time) {
      
         for (var i = 0; i < randNum; i++){
           Instantiate(Mines, screenPosition, Quaternion.identity); 
 
         //Instantiate(Mines, transform.position, transform.rotation);
         Timer = Time.time + 4;
         Debug.Log("Spawned Mines");
         
         }
     }
 }