I have a trogen virus

Any such popup message will be scam. Do not interact with such messages.

Avoid phishing emails, fake 'virus' alerts, phony support calls, and other scams - Apple Support

Force quit Safari from the  menu and reopen with the shift key held down. If that doesn’t work, disconnect from the Internet, delete the web site from History,open Safari, and then reconnect to the Internet. See link for other suggestions.

Safari -Tech support scam pop-ups

As stedman1 states, this is very likely a scam via popup window from your browser.

To further check your computer you could download the free/trial versions of MalwareBytes (www.malwarebytes.com) and ClamXav (www.clamxav.com) to perform scans on your computer. I use both these tools as part of my computer defense.

Bryan Dulock

Houston, Texas

If it actually says "trojan virus", these are pretty stupid crooks. A virus and a Trojan are two entirely different types of malware.

Most such scammers aren't known for their depth of knowledge about either malware or Macs.