You might want to check in Settings > General > Software updates, to see whether there is an iPadOS update waiting to be installed. (NB: It is always wise to back up your iPad before updating iPadOS)
Else: If your iPadOS is already up-to-date for that model:
You may want to try re-starting your iPad if you haven't already. (ie: Deletes temporary files, re-establishes connections, may update recent setting changes, and often restores order if something is not working as expected. If needed: See how to: Restart your iPad - Apple Support
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Apple support's dictation method for iPadOS 17: Dictate text on iPad - Apple Support
or
for iPadOS 18: Dictate text on iPad - Apple Support
and
only for iPadOS 18: Commands for dictating text on iPad - Apple Support