Level 6-4 (Mario vs. Donkey Kong: Tipping Stars)
From the Super Mario Wiki
The course is wide with multiple layers of platforms containing Blue Lift Rivets that help the Minis move from one platform to another. There are also many Pink Block spaces covering gaps between platforms, both horizontally and vertically. The Mini Mario starts on the bottom left corner, next to Mini Toad's door. The other Minis are locked inside capsules: Mini Pauline is found on the topmost platform in the left half of the course, between Mini Peach's and Mini Mario's doors; Mini Peach is at the bottom in the middle, under Mini Pauline's door; lastly, Mini Toad awaits near the right side of the stage, higher up. All three have to be rescued by the Mini Mario and brought to their Goal Doors to finish the level.
The M Coin is located on a platform immediately above Mini Pauline's door. A Blue Lift is necessary to access it.
Nintendo 3DS version
Wii U version