Hmm, Firefox doesn't have a built-in Export-to-file/Import-from-file feature for logins, so I'm not sure what you have or how to use it -- other than to open it and use it for reference when logging in to sites and saving logins again.

Maybe another support volunteer will have a suggestion on how to use it.

I think that only Firefox 56 can import a CSV password file using the Password Exporter Legacy extension. So easiest would be to download Firefox 56 (or 52.9.0 ESR) and install the extension in a profile and see if you can import the CSV file.

• https://support.mozilla.org/en-US/kb/install-older-version-of-firefox

Once you have the passwords in logins.json, you can backup logins.json and key3.db and copy these file to a profile used by the current Firefox release. Make sure you have removed key4.db (used in 58+) when present.

• http://legacycollector.org/firefox-addons/2848/index.html
• https://download-installer.cdn.mozilla.net/pub/firefox/releases/