I have a folder of MP3s, some of which date back to 1999, just a few years after the format was popularised. Most of them have utterly terrible names (think RIDEONAM.MP3). I think at this point they might even survive the heat death of the universe. And they’ll still be terribly-organised.
I’m currently making the move myself and I’ve had a really easy time with soundiiz.com and YouTube-dl with a Linux GUI. Basically soundiiz takes your playlist from one service and makes an identical one on another service. You move all your jams to YouTube and rip the audio out of them with youtube-dl. Here’s a wikihow with the deets