message pops up saying I have virus and a different message said I have a trojan

If these messages appeared in the upper-right-hand corner of the screen, they are probably Web notifications.

Here is how to block those in Safari.

Stop unwanted Notifications - Apple Community

If you use any other Web browsers, make the analogous preferences changes in all of them.

You might find this Apple article worthwhile reading:

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

Regards.

Those are scams, unless you manually uploaded a file to the website which produced them. There isn't a way for a website to scan a macOS system for malware, and even on Windows, someone using the computer would need to start the scanner.

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Yup its a 150% scam.