There are two ways. 1) copy the needed files from the profile to a thumb drive 2) use sync. Fast, easy, and you don't need a thumb.

You can use sync to share passwords, bookmarks, and history. Anything else may not be compatible between different browser versions or computer systems.

https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer Sync your bookmarks, history, passwords, add-ons and open tabs with another copy of Firefox. Learn how to set up Sync.

https://support.mozilla.org/en-US/kb/how-do-i-choose-what-types-information-sync-firefox We'll show you how to choose which types of information (bookmarks, history, add-ons, and passwords) to share across all your devices through Firefox Sync.

https://support.mozilla.org/en-US/kb/firefox-sync-troubleshooting-and-tips

https://support.mozilla.org/en-US/kb/sync-firefox-bookmarks-and-browsing-history-iOS Sync your passwords, history, tabs and other browsing information across your iOS, Android and desktop computers with Firefox Accounts.

My old computer is dead. no way to copy files from it. not very computer savy. not sure what sync is or what using it implies. can you clarify?

The sync feature helps you get your bookmarks, browser history, settings, etc. throughout all devices logged in with the same user ID. So, if your previous system's FF had the feature enabled, it should be brought back to your new system when you log in.

My old computer is dead

Sorry to hear that. If the hard drive is not damaged, what you could do is to have it removed and make it into an external drive. You will need to talk to a tech about this.

Do you have any backup files from the old system?