flac format to mp3 format?

Also, your approach is incorrect.

Assuming you're burning audio CDs, it's inevitable that you decode the files to WAV. So if you're working from FLAC, it makes sense to just decode them to WAV. If you transcode FLAC to mp3, you're going to lose audio quality. Afterward, those mp3s are going to have to get decoded to WAVs anyway, so you're wasting time and audio quality.

If you're burning a mp3-CD (data CD), then you should just use a tool like dbpoweramp to convert for you. I'd suggest foobar, but it doesn't work so easily right out of the box.

Jam it back in, in the dark.

Okay, for dbpoweramp you need to download the appropriate plugins for it.

http://www.dbpoweramp.com/codec-central-flac.htm

If you're burning an mp3 CD then decoding to mp3 is necessary. You should be able to fit three discs worth of audio onto a blank CD at 320kbps (alt-preset insane). I would recommend 320kbps since there's no audible loss in quality. However if you can't fit all three discs on the CD this way then you should choose a lower mp3 quality (obviously).

Make sure you name all of the files you are going to burn sequentially based on the order you mean to hear them, or put them in separate directories.

There's nowhere I can't reach.