Path to USB as source

I can click through my USB-device to play some music, but I would like to add all files to my sources to play them with my mpd-device like my files in my NAS. In the documentation I’ve read, that it is possible. Can somebody please tell my what I must type as Path to my USB-device, respectively how I can find out the path?

The UNC path for mine is

So \ hostname \ usb is the default path to the share.