From the Oracle documentation
Migration is the process of copying the schema objects and data from a source MySQL to Autonomous Database
I undestand it here as literal copying, without any change.
On the other hand, on the chapter on migration it says(if I understood it correctly) that before using it, it must be converted to Oracle format.
I don't understand whether this conversion to Oracle format, before using the Autonomous Database is a necessary step when using it.
This is the recommended approach (not mandatory) when performing a migration: you can resolve issues during these phases, and you can then inspect or modify objects to suit your needs.