Hello Kirk,
The cassette tapes are analog, so the bitrate does not apply.
Now speaking of .wav and .mp3 format, .wav is uncompressed .mp3 is compressed audio. You do not have to be concerned over what format your record with.mp3 is enough.
You can take a look here if you need a way of recording from your existing cassette player, then pair that with a free version of Audacity to record what you are playing on your workstation. Audacity works with PC or Mac. You can click here for a YouTube video showing you how to use audacity and the RCA to USB adapter in the previous link.