This is for you. You know who you are.
Here we have the conversion of an album's flac files to mp3 files using Audacity, an excellent freeware audio editting program. This can actually be done with multiple file types imported, but they'll share the same output format.
First you load a file, then Import all the files you also want to to convert. Use Shift + Click or Ctrl + Click to select multiple files. Choose Export Multiple and then choose the desired audio format you want to convert to (it's mp3 by default) and the destination you want the files to go to. After confirming that, you'll be asked to enter the info/metadata for each file, then the converting will start. That may take awhile, but once it's done, then that's it.