Thanks for the feedback! This is my first game jam, so it means a lot to me :')
I actually searched "platform games soundtrack" on google and found the majority in pixabay site. Here are the links:
Ending song - https://pixabay.com/music/happy-childrens-tunes-a-little-quirky-167769/
Menu - https://pixabay.com/music/happy-childrens-tunes-a-little-quirky-167769/
Main game - https://pixabay.com/music/acoustic-group-platform-8-262410/