Firefox indicated that my Firefox account was hacked. Please cancel my account. I haven't used Firefox in years.

Was this Firefox Monitor?

https://support.mozilla.org/en-US/kb/firefox-monitor https://support.mozilla.org/en-US/kb/firefox-monitor-faq https://monitor.firefox.com/

How did you get notification? Firefox doesn't send out such emails. Also Firefox accounts are just for forum posting it doesn't do emails.

Firefox is a web browser. Firefox Accounts as mentioned to you multiple times now is not only used on on support.mozilla.org as you can see in https://support.mozilla.org/en-US/kb/access-mozilla-services-firefox-account

Please inform me that you have closed/cancelled my Account