I think it’s solved. There’s no pop up messages, for now. Hope there won’t be any more. And I can successfully format my usb without leftover folders.

I was in a hurry today, so I took a second usb drive to take some files with me, and now I’m not sure if it’s infected as well. I’m hesitating to plug that one in. Will I need to repeat all of this again with the second usb?

Thank you for your help and patience.