What IO540 said, except with one caveat....
I have discovered my accumulation of cassette tapes
If you've seriously got a real collection, and are not just using the word "accumulation" to talk about, say, half a dozen cassettes, then I would humbly suggest you save yourself the time and outsource the job to a commercial conversion company.
Unlike you, they will have machines that enable them to multi-task and process multiple tapes at one time.