How to make a GUI bar that counts items collected

I want to display the amount of items the players collect in a bar on the screen but I cant figure out how to write that in javascript. T$$anonymous$$s is the code I have.

 var itemCount : int;
 
 
 function OnTriggerEnter(col : Collider){
     if(col.tag == "Pick Up"){
         Destroy(col.gameObject);
         itemCount ++;
     }
   
 }
 

  

`I would also like to have it displayed on the right upper corner of the screen because I have the health bar on the left side.