How to check if all clones in an area have been destroyed?

I am creating a tiny project where in an area, the player will need to push off all the clones that spawn periodically. I want to know if there is a way to test if all the clones have been destroyed so that the game can end. Anyone know how to test this? I will happily provide more details.

You could iterate through a List of GameObjects which contains all the clones, and check if any of them is still in the area. If you are spawning those objects, you could store them in a List, and remove them one by one, when they are getting pushed off. If the area is circular, you could use the Vector3.Distance function (with the distance being the radius of the circular area). If the area is a rectangle, you can check both x and z coordinates. But if the objects are being pushed off from the map (and they are falling), you can use the y coordinates as well. To answer this, we need to know more details.