Different 3d Model for different image targets.

Hello, I'm new to unity and i'm trying to build 3d animals to appear for coloring book. For this i'm trying to add models from asset store. But my model remains in screen even after the target image is removed and different 3d model is not appearing for different image target. I will be glad if someone give me link or some suggestion to get out of this problem. Thank you. Regards Sagar