I'm guessing that you studied something called collision detection in that chapter, so the simple solution would be to add one to your counter if the ring is within a certain distance of the cone when it lands. I guess the distance would be up to you, as well as the speed of the drop.
The answer involves converting the counter to a text string because that's what goes into a 3DText. There is a world function called "(what) as a sting" that you can drag in, and then replace (what) with the name of your counter.