McAfee

If these are sliding in the from the top right of the screen, a site you visited has given itself permission to send push notifications. Everything you're seeing is nothing but a scam.

Open Safari's preferences. Click on the Websites tab and then scroll down to Notifications. Clear any entries in the right hand window. You might find something similar in the Pop-up Windows heading below that. Block any you don't recognize.

Then if you want, uncheck the box below as shown here.

I personally can't think of any reason why I would ever want any website to push notices to me.

If however it isn't as Kurt advises, you can uninstall the application (if installed) per McAfee's website.

https://www.mcafee.com/support/?articleId=TS101226&page=shell&shell=article-view

Also look in Notifications System settings. You could have installed Adware that are putting them up.

Look for any apps you don't recognize.