Since I repeatedly had to search for that information. I searched with Google but all I got as an answer, even when using the search term EXTENSIONS, where references to copying the PLUGINS FOLDER.... I don't have any plugins and the folder is empty!
I figured it out by my self, and I'm thus informing my later me:
(and hopefully, all the other angry people, wasting hours, searching the net as well)
Start the new Waterfox once, just to make it create all folders.... than just copy the old folder PROFILE from the [Waterfox_Portable\Data] directory, from the old to the new "installed" instance of the program.
Thanks to myself for that Information
have a nice week...