“old gedcom” – yes. You will need that to import family tree data into a new installation.
“old mysql” – no. You should create a new database for the new installation, and leave the old in place until all is finished. If there are any tables that need to be copied from the old database to the new one (perhaps users?) then I can talk to you about doing that.
Remember – this NOT a normal upgrade. It is a way to safely upgrade when MANY upgrades have been ignored. Only necessary in your case when upgrading from a very old version with lots of modifications.