How do I get my mp3s from my hard drive to my speakers?

Paul doesn't believe in that.  You need a player.  A Roku, Sony Blu Ray, NAD CD player, most any streamer except Sonore and Metrum, etc.
With the Roku and a cheap monitor you can see what you're playing.
Can't play squat without a player.  Scott could have easily built one in the Sprout but no....

Good idea if you have a Spotify account.  Once you move up to lossless a streamer is recommended.

mahler123
Of course he can. That is NOT what he asked to do.
bsme85
You need a stinking computer for that. Pass.

rick
I too have gobs of thumb drives for auto. I play them exclusively during travel. The first thing that goes in a rental.
Don’t bother loading them on anything. Just plug them into the aforementioned devices and play. If you have a Samsung TV try that. Most streamers PLAY them. No mention of streaming. Ignore the man behind the curtain.
When you realize how much better lossless sounds you will be glad that you can play them too.
The Roku route is mp3 only and a cheap splitter will get it to the Sprout.
https://www.ebay.com/itm/254950382457?hash=item3b5c3a1b79:g:3YYAAOSwOQhgf98r
I’ve spent years upgrading my library from mp3 after I moved from computer to streamer players.