I installed Ubuntu 22.04.4 on a new system. I got .thunderbird copied from old and placed in the /Home/user folder. I placed a copy of .mozilla into same folder and when I go to run Firefox it doesn't know my passwords or bookmarks.
Ubuntu says the .mozilla folder goes in the /~ folder, so I put a copy there. Doesn't work! Another Ubuntu says it goes in the /user/.config folder. None of the places I've put it so far works.

What folder do I put it in? Or, what folders do I copy from the old system and where do I put them in the new system so I can have the passwords and bookmarks back again?
The .mozilla folder is huge, is it too large?

I can't speak to the folder location, but I can suggest an alternative.

For bookmarks, you can go to Bookmarks-->Manage Bookmarks-->Import and Backup and backup your bookmarks to a file, then, then import the file to the new system.

As for me, I've been using Firefox sync for years to sync bookmarks and plugins and have never had any issues with it.

Don't know about passwords, as I use keepassxc for them, and the keepassxc database is portable.

In ubuntu firefox is a snap package, and snap uses chrooted environments for each snap package mounted as separate loop devices, home for firefox will on one of these devices. You can either locate it and place .mozilla folder there or purge snap from your system and install firefox from other sources. Debian repo can be found here here https://sourceforge.net/projects/ubuntuzilla/ and binaries are available on mozilla site https://ftp.mozilla.org/pub/firefox/releases/ Also I read that you can configure home location in snap, but I prefer elimination, not customisation.

Well, that explains a lot! Thanks. I found firefox would not actually uninstall. Synaptic said it was, but the launcher was still accessible. And after I sort of got it working, I still couldn't get the bookmarks to show in a menu. Brave seemed to be working just fine. Since my wife doesn't like changes I'm staying with Ubuntu.

Thanks for the help!