Finding audio clips in a specific folder if it is exist (Android)

I'm pretty new in unity. So I want to learn the easiest way if there is one.

In fact it will simply check if there is a folder like "GameMusics" in the file system of my android device. If there is, it will play the music in it in a loop. If not, it will play the music in assets.

If you can help, you may have helped game development, not much but a little bit.