You can open the menu and view the currently collected U disks (songs) under Collection → USB Songs. Then you can search the song name on the music website and play it.

The USB flash drive in this game is a small USB flash drive with red and green indicator lights. Each time a USB flash drive is found, a song can be unlocked. When you get close to the location of the USB flash drive, it will be marked with a special icon on the minimap. But by default, it will not be marked on the map. You need to stay online and connect to your Ubisoft account. When you leave the Free Arms Island, you will get 300 Far Cry points. You can use the points to purchase and collect the map through the store. Markers are displayed on the map.

Don’t worry about missing any USB flash drive. After completing the main story, you can return to any area to explore freely. It is best to clear all the anti-aircraft guns on the map first, and then you can use "airdrop" to quickly move to the location of all USB flash drives.