As far as I know, this will be two separate processes. You will need a transcription service to “listen” and transcribe the material. There are services: speedscriber.com, simonsays.ai, rev.com to name a few with different levels of price and service. Then you get back a file, maybe a subtitle file like and .stl, and then you can take that and cover them in to FCPX titles. Apps like Subvert, or X-Title Importer are good ones to start with. Once the titles are in FCPX, you may have to adjust formatting.