I was notified that my MacBook has 3 virus

There are several items that you can get via browser that have not affected the macOS.

Unless you act irresponsibly and import something untoward, then you could get 'it.'

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

https://support.apple.com/en-us/HT204759

• Phony "tech support" / "ransomware' popups and web pages - Apple Community

https://discussions.apple.com/docs/DOC-8071

• Malwarebytes for Mac - is 'antivirus' replacement

https://www.malwarebytes.com/mac/

• Using EtreCheck - Apple Community

https://discussions.apple.com/docs/DOC-6172

• EtreCheck - more info/pages & download

https://etrecheck.com/index

There may be some other issue affecting the graphics or showing artifacts;

you may also start the Mac in Safe mode to see if that helps. ~ Then restart

normally. This can help in troubleshooting w/ some minor issues resolved.

• Use safe mode to isolate issues with your Mac - Apple Support

https://support.apple.com/en-us/HT201262

Natalie,

Apple will never pop these dialogs, or redirect you to a website. Thus, you can be certain that no matter what extent the criminals behind these make them look like official Apple sources, they are not, and do not interact with them. Just quit your browser without clicking any button, including Cancel.

If you are using Safari, launch it again by pressing the shift key which will avoid loading that site again. Clear your history, which will also clear your cookies. In Safari Preferences : Advanced panel, select Show Develop menu in menu bar, and press option+command+e to clear your browser cache. Quit Safari and launch normally. You may need to run Malwarebytes per K. Shaffer's post.

I refuse to revisit any website where this trash originates.