[Koha] Upgrading Koha >> several versions

Hi all, I'm currently running a couple different versions of Koha, and I'm going to try and do a mass upgrade to the newest version this summer. Koha version: 17.11.18.000 OS version ('uname -a'): Linux Pine 3.16.0-4-686-pae #1 SMP Debian 3.16.51-3 (2017-12-13) i686 I'm sure my servers/versions are going to require a database dump / restore, and maybe a copy / migration of my "site" files as well. Is there a "step by step" how-to document anywhere ? Something with small words and pictures would be perfect for me .😬 Thank you. -S