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.
Stamp[]
The Stamp is found near the end of the level in a cave below a single Koopa Troopa.