Pop up virus on MacBook

There a re no viruses on your Mac. Macs do not get "viruses". It's a scam to get your personal information, do not rely or furnish any info. No one can know what's on your Mac, not even Apple.

If the pop-ups continue Force Quit Safari ( command + option + esc keys).Then restart Safari holding the Shift key. If you still have problems Empty Caches (Safari menu > Preferences > Privacy > Remove all website data. (This will also remove history if you do not want to remove History open Safari Preferences > Advanced and check mark “Show Develop Menu” then choose “Empty Caches” from Develop Menu ).

Then go to Safari Preferences > Extensions and check there. If there is an extension delete it.

If the problem persists then download and run Malwarebytes. Malwarebytes was developed by one of our own colleagues here in ASC and is about the most proven anti-malware software for Mac.

Sounds like you have adware installed on your Mac, please do as MacJack suggests.

Have you done what MacJack suggested yet?

What were the results?