How can I move my preferences and extensions to a new computer? Have I done it successfully?

Question

My old computer crashed. I've set up the new computer. I copied all the profile files/folders to the profile on the new computer in both the local and roaming folders.
Does this copy over my preferences and extensions? The help pages say they don't tell how to copy those since they can be the cause of problems. However, they weren't problems. So I want them copied. The extensions folder on the old computer was empty (I don't recall if It'd had any installed or just bookmarked some.) I remember making some specific preferences changes in that "advanced" file (that worked fine afterward.)
So with what I did, did I successfully copy everything over? If not - where are the extensions and preferences so that I can copy them over?
Bonus big question - is there a way to merge my old browsing history with the history on the new computer that I used for 10 days? Right now I set those 10 days as a separate profile, so I can save and go check it if I really need to.
Thanks!

Answer 1

Take the good profile and copy it to the new computer. Also copy all
of your add-ons. On the new computer, start Firefox. Once it is running,
shut it down. Then transfer the information from the old profile to the new.
Thess add-ons can save all add-ons into a single folder for transfer.
These add-ons can be a great help by backing up and restoring Firefox
'''[https://addons.mozilla.org/en-US/firefox/addon/febe/ FEBE (Firefox Environment Backup Extension)]''' {web link}
FEBE allows you to quickly and easily backup your
Firefox extensions, history, passwords, and more.
In fact, it goes beyond just backing up -- It will actually rebuild
your saved files individually into installable .xpi files.
It will also make backup of files that you choose.
'''[https://addons.mozilla.org/en-US/firefox/addon/opie/ OPIE]''' {web link}
Import/Export extension preferences