I think that a pcv is a ZIP archive, so you should be able to inspect such a backup in an archive file manager. Note that such old backups are of no use and might cause issues as files are incompatible and current releases no longer have the code to upgrade to currently used schemes.

You can copy certain files with Firefox closed to the current profile folder to transfer or recover personal data. Note that best is to avoid copying a full profile folder.

• bookmarks and history: places.sqlite
• favicons: favicons.sqlite
• bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
• cookies.sqlite for the Cookies
• formhistory.sqlite for saved autocomplete Form Data
• logins.json (encrypted logins;32+) and key4.db (decryption key;58+) for Passwords saved in the Password Manager
  key3.db support ended in 73+; to use key3.db in 58-72, make sure to remove key4.db
• cert9.db (58+) for (intermediate) certificates stored in the Certificate Manager
• persdict.dat for words added to the spell checker dictionary
• permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
• sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

This didn't solve my problem but thanks. my problem Was solved though. I was taken to some site and asked to 'sync' my firefox with a another device. i thought that i could see if i had firefox on my phone or somewhere and see if my info was on there. the phone is also new and i hadn't installed firefox on it so i had little hope, but as soon as i pressed 'sync' new windows started to automatically open up and my add-ons were being installed. i was pretty startled. then i checked my bookmarks and they were all back. OH MY GOD. Now i just have to find a way to save them all so this doesn't happen again. i think MozBackup is failing me

This didn't solve my problem but thanks. my problem Was solved though. I was taken to some site and asked to 'sync' my firefox with a another device. i thought that i could see if i had firefox on my phone or somewhere and see if my info was on there. the phone is also new and i hadn't installed firefox on it so i had little hope, but as soon as i pressed 'sync' new windows started to automatically open up and my add-ons were being installed. i was pretty startled. then i checked my bookmarks and they were all back. OH MY GOD. Now i just have to find a way to save them all so this doesn't happen again. i think MozBackup is failing me

Hello! I think what happened there is Firefox Sync, if you've created a Firefox account before and turned on syncing, your data is stored in your Firefox account via servers. More info: Mozilla account - Managing account data Access Mozilla Services with a Firefox Account