Super Bell Hill is the second level in Super Mario 3D World, and is also know as World 1-2.
The first Green Star is found in-between two sets of cloud platforms.
The second Green Star is found in a mystery box located right after the checkpoint, near the top of the screen. It is earned by defeating both Koopa Troopas
The third Green Star is found in the middle of a Goomba
Stack near the end of the level.
The Stamp is found near the end of the level in a cave below a single Koopa Troopa.