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

Well how do I ? right now I have a PS Audio Sprout 100 with built in DAC.
I am missing something here.  Why can’t he connect the computer to the DAC and use iTunes or Windows Media Player or whatever he has to play the files?  I haven’t played files from a computer for a couple of years but that used to be the drill...
You don't need an additional player or hardware. You need a program or software like itunes, jriver, audionirvana, foobar2000 and so on. See what mahler123 said.
So I can load the files on a tablet etc and USB them to the DAC.
I want to stay very far away from the Apple universe. And at this point not interested in streaming. I have been running thumb drives to my receiver in my cars for many years.
Of course he can. That is NOT what he asked to do.
You need a stinking computer for that. Pass.

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.
I’ve spent years upgrading my library from mp3 after I moved from computer to streamer players.

I dunno...  Plex?  foobar2000???  There are actually just a few programs that seem to do the job - just manage the connection from hard drive (local?  network?)  to your preamp/receiver/whatever.  Heck, a number of receivers, etc. can be set up to connect to & play stuff on network drives - if you can present your source on the hard drive to whatever you use it's become surprisingly easy to play 'em.