Hey! If you've purchased the tracks then you're free to use them in any project you like, as much as you like! Since you purchased them through the itch.io asset store, I don't believe you need any license documentation as anything purchased in the itch.io assets store gives you full commercial non-exclusive rights.
This is the case with Unity, Unreal and other asset stores I sell my assets on, and despite searching quite hard I can't find anything that says itch.io is any different, however if have a link to information that says otherwise, just let me know and I'll sort it out for you! :)
Let me know if you have any other questions!