Different versions of Firefox are known to change how they store data.

Sync 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.

Once you are done with sync, you can remove it if you want.

Thanks for the reply. The only issue with this method is that i am giving all my logins to mozilla. Not a very comfortable idea.

The sync data on the servers is encrypted by your e-mail and a password you choose.

Firefox 52 uses key3.db for the key file. In Firefox 73 support for key3.db has been removed, so you will have to install an intermediate version like Firefox 68 and use this version with its own profile to migrate logins.json and key3.db from 52 to logins.json and key4.db that can be used (i.e. copy these files to the 86/87 profile. in a release profile. You can also consider to install Firefox 52 and update this version until you reach the current release to ensure proper migration of all files.

All Firefox releases on the Mozilla server:

• https://download-installer.cdn.mozilla.net/pub/firefox/releases/
• https://support.mozilla.org/en-US/kb/custom-installation-firefox-on-windows

Use the profile manager to create a new profile although Firefox 68 might do this by default.

• https://support.mozilla.org/en-US/kb/profile-manager-create-remove-switch-firefox-profiles