There are not many ways to convert an audio file to text without paying a lot of money.

Microsoft 365 provides this service:

Open a new document, then click on the transcribe icon in the top right corner

Transcripts can be downloaded from YouTube, using DVDVideoSoft.  They provide a Free YouTube to MP3 Converter, which downloads the audio files from single videos, playlists, or entire channels.  The downloads have the suffix ‘.srt’, and have to be converted to text files – I use https://subtitletools.com/convert-subtitles-to-plain-text-online.  The ‘.txt’ files created are easy to view, but formatting and searching for text is best done if they are then converted to ‘.docx’ format using MultiDoc Converter