removing files that are suggested to be dangerous like nuT......

Upon starting my older MacBook Air a pop up window appeared and suggested that I move a file nuT... to trash as it was dangerous. When I clicked ok the window just kept reappearing. When I pushed cancel same thing. When I went to find this file with File no luck. I tried to follow the how to remove NBP what ever and I could not even find the start up or launch.. At a Loss Afraid to open any important or personal items such as Quickbooks