factory reset-saving contact information

How do I back my contacts and all other information from my phone so that I can do a factory reset? My grandson downloaded a game sometime ago and I cannot get rid of games popping up on my screen all the time. No matter what I select games and advertisements pop up. I've tried to clean the google play store, play services and books but get no relief from the popups. And I've tried deleting the games but I cannot. My only resolve I suppose is to do a factory reset but I do not want to lose all my contacts and numbers. I would be lost without them. Thanks for your help