ownCloud 9.1.5 to nextcloud pointers and tips needed

I have ownCloud 9.1.5 running on Debian on an Intel Atom computer and would like to move to nextcloud. I know that starting with the correct version is essential. I would appreciate if someone can tell me which version of nextcloud to use to transition and then update to the latest version of nextcloud (11?).

Any pointers or links on how to proceed would be appreciated.



Thank you!