Use the Springboard to reach the Roulette Coin Blocks and the Roulette Block above the Checkpoint Flag. While you bounce, take care to avoid the Red Spike Buzzy patrolling each Block.
The first Star Coin is located in a hidden area. To reach it, you must enter the lower pipe at Point 2. Stomp the Buzzy Beetle near the upper pipe, then toss its shell at the POW Block near the moving platforms. The chain reaction clears a path to the lower pipe.
When you reach the hidden area, stomp the Buzzy Beetle and use its shell to clear the Piranha Plants on the left side of the room. Follow the shell down the passage to find the first Star Coin.
The second Star Coin is enclosed within the Blocks at Point 3. Stomp the nearby Buzzy Beetle, then carry its shell to the Blocks above the Star Coin.
Throw the shell to the left. When the shell strikes the POW Block, the impact clears a path to the Star Coin.
When you pass through the Red Ring at Point 4, red coins appear in a circle around you. Hop around the moving platforms to grab them before they vanish.
The third Star Coin is floating high above the ground. To find it, jump from the moving platforms to the Blocks at Point 5.
Jump along the Blocks as they lead you toward the cavern ceiling. Use the POW Blocks to defeat the Red Spike Buzzies along the way. When you reach the end of the Blocks, make a running leap to the Star Coin.