You're asking similarily: "I have this ball here, but it doens't fit to the box-shaped slot or I have these bananas here, but I want them to be oranges!"
Without any further infos, I can't help you. If you wish to transliterate spoken audio to text, please try searching appropriate tools for that, OBS alone is streaming software, it doesn't do any other conversions than remux a mkv to mp4.