Your system is infected with 3 viruses!

Hello!

The good news is that it is not. This is Malware/Adware that tries to scare the user into thinking they have been affected, so they will download and pay for their app/program or in order to gain your personal information.

HT203987 has some good steps for these popups

Apple does recommend Malwarebytes but only the free version, you should not or have to pay for this service. Once you download, run the scan and if any threats are found, you can remove them from your Mac for free: https://www.malwarebytes.com

I would not recommend installing any antivirus protections (i.e. AVG, Norton, etc) as it can actually slow down your Mac and cause issues. Your macOS keeps you protected, so it is good to make sure you are always up to date: https://support.apple.com/en-us/HT201541

EMAC2011 wrote:

I keep getting this pop-up Your system is infected with 3 viruses!

That's the fewest number I've ever seen reported by those scams.

Ignore it: Phony "tech support" / "ransomware" popups and ... - Apple Inc.

It is a scam phishing attempt.