How can I stop Firefox pop ups warning about viruses and Windows updates?

Can you share a screenshot?

Also check: 1. Remove allowed notifications in Firefox Goto Menu ☰ > Settings > Permissions and data find Notifications and look through the list of websites for any unfamiliar sites. Select and click Remove Website. Click Save Changes.

2. Also check your extensions click the Μenu > Extensions and themes (or Ctrl + Shift + A) > Extensions. If you see anything you did not install click the three dots next to it and select Remove.

I am getting constant pop up "alerts" on the right side of my screen that block my view. When I close one another pops up. It's very annoying. All of them have the Firefox logo and name in the upper left corner. Thanks.

https://support.mozilla.org/en-US/kb/push-notifications-firefox#w_how-do-i-revoke-the-notifications-permission-for-a-specific-site

The small popups on bottom right corner of Firefox window are not from Mozilla nor the Firefox web browser but rather are web push notifications from site(s) you have allowed to send you notifications. You can revoke the sites as per kb article link.