There’s a Springboard on the platform at Point 1. Leap up to the platform and grab it, or hit the ? Switch below the platform to drop the Springboard down to you.
The first Star Coin is floating at Point 2. Use the Springboard to bounce up and grab it.
When you reach Point 3, use the Springboard to bounce through the gap in the ceiling. Wall jump to the ledge, then enter the red pipe above you to find a hidden room.
The second Star Coin is surrounded by Blocks. As you pass under it, smash the Blocks to clear a path to the Star Coin.
The third Star Coin is sealed behind a wall. Use a Bob-omb to blast a hole in the wall, then grab the Star Coin before the lava reaches you.