At max, two full work weeks for a lightly trained amateur to transcribe 42 hours of decent but not great quality audio. A professional could do it in near realtime.

For me, it is notable that this is notable for you. This used to be as ubiquitous of a profession in modern organizations as typists were. Many people's entire job was going to meetings and/or listening to calls, transcribing the conversation, not just taking notes.

Professional stenographers transcribe in realtime with phonetic markers and everything. Even lightly trained transcriptionists can transcribe 1 hour of audio in 1.25-1.5 hours of wall clock time. For an amateur, you could probably get to a 1:2 ratio within a few hours. It's at max two full weeks of work.