Hi, I’m looking for a simple,easy-to-use program to convert .MIDI files and .WAV files to .MP3 files. I have a Windows computer.
I’d like to save these files to a USB and/or SD card.
Audacity is a good software. You can also convert it with "Any Video Converter"
A MIDI file uses hardware to play the music; you'll need to re-record the midi in something like Audacity to save it as an MP3.
See the article - How to Change a Midi File to a Wav or MP3 File
Audacity is a better tool.
Also,some other tools are also mentioned previously asked by other person -