Do U Stack Up?
From the Super Mario Wiki
The first part of the level initially features several Hoppers at higher ground behind partial cover, but from the end of the second turn onwards, additional Hoppers appear. Mario and co. must take out five Hoppers to win.
The next part of the level introduces the Smasher enemy, and while only one initial Smasher appears, more appear at higher ground just ahead. Mario and co. must reach the area shaded in yellow to win this part of the level.