Most addons store their database in ADDONTABLE.db, but not necessarily always there. You will need to know what each addon's name and table is in _G, or otherwise use AceAddon:IterateAddons() to iterate over all the Ace3 addons and see if any of them used AceDB.
The SetProfile just sets addons to that profile name if the user has already created a profile with that name. It won't work on Addons that don't have the Profiles.
Note that when you call SetProfile() with the name of a profile that doesn't already exist, AceDB actually creates that as a new profile and then sets the current profile to it. So watch what you are doing..., you may end up switching profiles to a completely new profile that you didn't want to.