I just use a cassette adapter. https://www.amazon.com/INSTEN-Universal-Cassette-Adapter-Smartphones/dp/B00CRBA9D8

Just wondering if something like this could convert mp3 to a cassette tape. I assume so since most things go vice versa but idk.

Not in this case. A lot of hand-held cassette players are play-only. They don't record.

I expect you're engaging in overkill looking to a "converter". You don't need a USB connector or custom software. Just run a stereo mini jack from the headphone jack on your computer to the input of any cassette player with a recording head. (lo-fi example)

Though, why do you want to transfer things to cassettes anyway? Most of the time you'd be better off with a portable MP3 player and a cassette-deck adapter.