This stage is Double Cherry Pass (2-5). This complete walkthrough will provide you with a 100% video playthrough and a screenshot of where you can find all the green stars. We will also note a secret 1 UP.
Game Play Walkthrough Video
Green Star 1
Head to the right until you see a vertical pipe. Break the wooden crates to the right of the pipe to reveal the first Green Star. Remember to break the left crates too for a double cherry.
Green Star 2
After progressing through the stage, you will hit two switches. You will need to place a Mario on each of the switches to get the green star.
Green Star 3
At the part of the flagpole, head to the left side. You can raise the platform if you have four copies on the platform. The platform will raise up and you will obtain the last green star.
After getting the second green star. Approach a wall with three question marks. Place a character on top of the block while having another bump the blocks. The blocks will rise up for you to obtain the stamp for the stage.