This level is one of the shortest levels in the game. The entire level is built with Grab Blocks, which can be used to defeat the Lakitu hovering above. Upon starting, you will find a yellow Baby Yoshi who hatches out of his egg, and a grey P Switch that can optionally be used. By feeding the Yoshi five times, it'll grow into a grown up Yoshi. Defeat the Lakitu above and use his cloud to fly up to an area with a keyhole and a key that will take you to Star World 4. Otherwise, just run into the Goal Pole that's just right there.
The GBA remake of the game adds in five Dragon Coins. The first Dragon Coin is right at the start on three grey blocks, the second Dragon Coin is on the highest point of the Grab Block "staircase", and the rest of them are behind the Goal Pole. The player can use Lakitu's cloud to fly up the area with the keyhole and keep going right to bypass the pole and collect the three.