How to get rid of online virus?

Okay so I got a pop up from apple security saying I had 8 virus and if I didn’t do something about it my phone was going to crash. I looked up how to get rid of virus and it said clear search data and I did. Than I also took a step farther and backed up my iPhone completely and reseted my whole phone. Today once again when I was on safari it popped up again saying I still have 8 virus and I really don’t know what to do. What am I suppose to do to get them cleared ??? Also can the virus transfer to my iCloud when I backed it up and that’s why there still here? Because I backed up my phone when I had viruses on them ?