Secret Course 08
From the Super Mario Wiki
The course starts with the first Bonus Medal immediately in plain sight right before the first Bullet Bill. Immediately after this is the second Bonus Medal and another Bullet Bill. The third Bonus Medal is after that and is a little higher, but can be collected by jumping off the Bullet Bill. The fourth and fifth Bonus Medals can be obtained by jumping from the three Bullet Bills right before the Goal Pole.