From the Super Mario Wiki
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The course features eight minis. It is one of the three courses (aside from Room R-10 and Room R-11) that need to be completed in order to unlock the option to change most levels in the game so that they feature a mix of all types of mini toys.
The minis start in different parts at the top of the level, with the Goal Door being located in a tunnel at the bottom right. Using Pink Blocks, the minis have to be navigated to the goal while protected from spikes on the ground.
Mini Mario Card
The Mini Mario Card is on a girder platform towards the bottom left. The player can help the minis reach and collect it by leading them to the card with Pink Blocks. A yellow Box Spring under the Mini Mario Card can also be used to bounce the minis to it.
The M-Token is located in an alcove in the bottom left. Pink Blocks are needed to reach it.