Do X if all pickups are gone

Hi, newbie here so I’ll try to make this clear.

I’ve been following along on the Roll a Ball tutorial and wanted to do something a little different/expand on it. So what I want to do is make it so the game checks all the pickups in an area, sees that they are gone, and then does something(Like open a door a spawn a teleporter).

I have the pickups already set up, but no idea how to run this “Check area” script. Also since this is for a college class, I’m using an older version of unity, version 4.3.3

Thanks in advance if someone can help me.

tag your pickups in unity . i will cheek if there is any of them in Start function for now but you can edited so you can use it when click a button or keep cheek @ run time in Update function so you will get the idea :

 void Start(){
    		if (GameObject.FindWithTag ("pickups") == null) {
    			print ("no pickups found");
    		} else {
    			print ("pickups found");
    		}
    	}