For media already on CD, and that was not commercially produced, you need to check what format is actually used on the CD itself. A very great many will have used MP3 to begin with.
VLC is good for saving out existing audio files from one format to another. I haven't done that in a very, very long while, as I've been using MP3 exclusively for myself for years now.
As far as converting audio tape to MP3, when I've needed to do that I've used Audacity. I simply play the tape while Audacity "listens and records" then, once it's done, save the Audacity project out as an MP3 file. At one time you had to manually add the LAME libraries to Audacity in order to do this, but I believe they may "come with" these days. Someone who uses Audacity much more frequently than I do, and who's installed a recent version, can speak to that.
I have a cassette tape of my grandfather talking about the family history that I digitized using the previously mentioned technique.
Brian - Windows 10 Pro, 64-Bit, Version 1909, Build 18363
Tolerance is the positive and cordial effort to understand another's beliefs, practices, and habits without necessarily sharing or accepting them.
~ Joshua Liebman