How to transcribe audio to text

You can enable Dictation here:

Settings → General → Keyboards → Enable Dictation

At the bottom of your keyboard, you will see a microphone. Tap it and talk. What you say will be written down. If you are looking for an opportunity to listen to e.g. music and auto write down the lyrics, this is not the solution.

You can read more about Dictation here:

Use Dictation on your iPhone, iPad, or iPod touch - Apple Support