If you want mp3, just tell youtube-dl that:
youtube-dl -x --audio-format mp3 https://www.youtube.com/watch?v=uWusmdmc0to
will get you an audio version (-x, short for --extract-audio) in or converted to mp3 (that’s the --audio-format option). youtube-dl will automatically pick the best quality and most appropriate format.
Note that the listed qualities are just guesses. In practice, opus is superior to anything else, but vorbis is picked for compatibility (refer to this related answer of mine for more details), so that will be picked.
While you can use -f to select a particular format, this is intended for people who want lower quality because of limited bandwidth or storage space, or for debugging. By default, youtube-dl already downloads the highest quality.