The second level of this world is a dark level, meaning you really won’t be able to see where you’re going. If you have a Fire Flower, though, that can help a little bit, as you will be able to see where your fireballs are heading. At the beginning of the stage, follow the path until it bends around, then get the power-up (Fire Flower) from the ?-Block. The big room you will enter is filled with Switch Panels, so step on them to turn them from blue to yellow, allowing you to continue. Keep going through more hallways and another room with Switch Panels, then when you get to a circular room with some unlit braziers.
You will need a Fire Flower here, since lighting all four braziers will net you Green Star #1. The next hallway will house the Checkpoint Flag, so touch it and get a power-up from the ?-Block. Before you enter the next room with Switch Panels, there is a small tunnel on the right side, leading to Green Star #2. The next Switch Panel room will have a Fire Piranha Plant on a moving platform in the middle. When you get to the bridge sitting over lava, take the platform to the right, but jump off on the right side, where you’ll find the Stamp.
The final room of this course will have Switch Panels in the four corners, along with a bunch of enemies and platforms moving in the middle. The first thing to do, if you have a Fire Flower, is to clear the room of enemies, as that makes turning the panels much easier. Once you’re done, the door will open up, leading to a green pipe, but don’t take it just yet. Along the wall, behind the pipe, you can find a hidden ?-Block. Hit it, then do a Ground Pound jump to the alcove above it to find Green Star #3. Go through the pipe now to arrive at the Goal Pole area.