1. for detailed instructions see Recovering important data from an old profile
2. if your history and bookmarks are important to you manually export them to files somewhere safe, because you could loose or overwrite them, and any auto backups while sorting out the profiles and add-ons. You may want to backup other profile information although it is probably easy to find any add-ons again, and if necessary, re-install from scratch especially if you have their sites bookmarked.
3. Next create an additional profile, disable rather then deleting any unused profiles, until you are sure you have got the situation as you like it. Again some deletions will be hard or impossible to replace. See Profile Manager - Create, remove or switch Firefox profiles

I did sidestep your original question but

■ copying addons can cause problems

• see the caution in the info I linked to in paragraph 1 of the above post it says
• Note: Because your preferences and extensions are often the causes of problems, this article does not explain how to copy these between profiles ...

■ I believe it can be done and is explained on the mozillazine. But I am currently getting 503 errors from that site so can not find the article to link to. I have not tried it myself, but I suspect method entails direct manual editing of profile file content.

■ While mentioning cautions, remember when creating folders it may be wise to use empty folders.

• Firefox tends to delete all folder content when profiles are deleted.
• Also note firefox use of profile paths containing random number strings,
• and the folders themselves are likely to be hidden folders.

P.S. if you are still interested in manually moving or copying Add-ons between profiles then these KB MozillaZine articles may be of interest:

• Transfer data and addons
• Installing manually