Data base migratrion

O/S: Ubuntu
Ver Mastodon: 3.4.5

logged into my mastodon instance and found this message

There are pending database migrations. Please run them to ensure the application behaves as expected
Can someone point me to the non-docker instructions

And a side question could there be issues if I upgrade Ubuntu to 20.04

Instructions are described in Upgrading to a new release - Mastodon documentation as well as in individual release notes.

Log into the user you use to run mastodon, and run RAILS_ENV=production bundle exec rails db:migrate then restart the Mastodon services: as root, systemctl restart mastodon-sidekiq mastodon-streaming && systemctl reload mastodon-web