Collect the indicated number of medals to unlock the indicated Medal Swap bonus:

Bead Line: Six medals
Course 1-8: Nine medals each
King Dedede: Twenty medals
Life Boost: Seven medals
Life Boost: Twelve medals
Life Boost: Fourteen medals
Meta Knight: Twenty-five medals
Song One: Three medals
Song Three: Three medals
Song Two: Three medals
Tropic Line: Six medals
Zebra Line: Six medals