I'm making a Radio and you put in an id and click buy and it should prompt you to buy it to play the music. How would I make it buyable multiple times I cant find anything.
There is no such thing as a "Gamepass that can be bought several times".
If you want to provide in-game purchases that can be bought many times, you have to use a Developer Product.
Look down for more info
Go to your Roblox Develop Section
And you will see your games. Click the icon that looks like settings(or more) that you want to add your Developer Product.
Click Configure Game > Click Developer Products > Create new.
Click here for more info on Developer Products, don't forget to accept the question!