A better known solution is Nuance Software's "
Dragon Naturally Speaking". It is a great deal more advanced
in the interpretation and adaptation-to-voice issues than are most
Speech-to-Text machines, but it doesn't sell for $39, either ...
prepare to pay $100 - $300 depending on which version you purchase,
and where you purchase it.
If you wish to convert existing audio files (WAV, MP3) to
text, as opposed to converting a live narrative, this may not be
your cup of tea. In that case, perhaps the earlier suggestion would
work better(???). Good luck.1
P.S. The suggestion to "Google" for the answer to your
question is probably the best idea. Use Google to find a list of
possible solutions, then download the "trial" versions, and select
the one that works best for you.