How to make ammo reffil on pickup

this is my script for gun

 static var ammo = 30;
 static var health = 100;
 static var maxAmmo = 120;
 var key : String = "mouse 0";
 var bullet : Rigidbody;
 var speed : float = 1000;
 
 function Update () {
     if(Input.GetKeyDown(key)){
         if(ammo > 1){
             shoot();
         }
 
     }
 }
 function shoot(){
     var bullet1 : Rigidbody = Instantiate(bullet , transform.position, transform.rotation);
     bullet1.AddForce(transform.forward * speed);
     ammo --;   
 }
 function OnGUI () {
     GUI.Label(Rect(10,10 , 250, 250 ), "ammo:"+ammo) ;
     GUI.Label(Rect(80,10,250,250), "hp:"+health);
 }
 
 
 and this is my script for ammo
 
 var playerTag = "Player";
  
 function OnTriggerEnter (col : Collider) {
     if(col.tag == playerTag){
         shoot.ammo = shoot.maxAmmo;
     }
 }

I want that ammo in box wich is 120 and then + current ammo wich is ammo