Migration from Owncloud 8.2 to Nextcloud 9 plus distro upgrade

Dear all,

I want to ugrade my old version ownCloud/Ubuntu to a Nextcloud/Ubuntu server, but I have several doubt.

I start to ownCloud 8.2.11 (last 8.X for Ubuntu 14.04 LTS) to arrive to Nextcloud 10.0.x (Ubuntu 18.04 LTS) and now I’m here:

ownCloud 8.2.11 (Ubuntu 14.04 LTS) --> ownCloud 8.2.11 (Ubuntu 16.04 LTS) --> ownCloud 8.2.11 (Ubuntu 18.04 LTS)

ownCloud stopped working after first distro upgrade (I think because has removed MariaDB and written over Apache config files), sorry I’m not a Linux expert…

From https://nextcloud.com/migration/ I imagine I have to complete the path through
ownCloud 8.2.11 (Ubuntu 18.04 LTS) --> Nextcloud 9.0.x (Ubuntu 18.04 LTS) --> Nextcloud 10.0.x (Ubuntu 18.04 LTS)

In this situation can I simply use migration tool? Do I lost my user DB (4 users) or can I recover it?

Can someone give me ad help/advice on how to complete the upgrade?

Thanks a lot.

For example, a question is: what I need to check on ownCloud installation as prerequisite for a migration procedure? DB, Apache & PHP config files?

In alternative, a fresh Nextcloud installation with the goal to mantain files&users is mush more easyer or not?