That isn't from FF that is sites that one goes to that popups ads. That is most likely a fake site mimicking Mozilla. So you should back track what you did to get there and that will tell you where it started.

This is a scam to try and trick inexperienced Windows users.

Firefox is a web browser and not a antivirus scanner. Also Mozilla does not charge for anything and they do not do any one on one support by phone, chat, or email.

https://support.mozilla.org/en-US/kb/avoid-and-report-mozilla-tech-support-scams

Thank you!

If you get a pop-up message asking to update Firefox or plugins or scanning for malware then such a message is likely a scam and you should NEVER respond to such an alert to avoid getting infected with malware.

• only update Firefox via "Help -> About" or by downloading and installing Firefox from the Mozilla server and never via a pop-up or link on a web page.
• plugins should only be updated via the plugin itself or by visiting the home page of the plugin.

See also:

• https://support.mozilla.org/en-US/kb/i-found-fake-firefox-update