Enabling player to pick their own music

I am working on a 2D game for android in Unity3D, and i would like to add a feature that allows player to select their own music to play in background. Some kind of UI that shows you all the mp3 formats in you phone and you can pick which ones to play.

I am a beginner programmer, i know how to make simple UI, but i have no idea how to construct something like that.

Thank you for any help on this topic.