This stage is Searchlight Sneak (5-7). This complete walkthrough will provide you with a 100% video playthrough and a screenshot of where you can find all the green stars.
Game Play Walkthrough Video
Green Star 1
Shortly within the stage, you will see a green star in mid air. Bring a spring from a stunned spring monster to jump higher.
Green Star 2
After getting the stamp, the green star is hidden inside a mystery box behind a cracked wall. Lure the bullet bill to hit the wall to break it. Enter the room and grab your second green star.
Green Star 3
Lure the bullet bills to break the bricks holding the last green star. You will have to time your jumps and lures perfectly to break the bricks. It is the easiest if you jump on top of the breakable pieces.
You won’t miss it, the stamp is available for you to grab after the first green star.