I opened a file which could be infected

I opened a file which could have been infected. So I made a back up in iTunes and put all my settings back to the factory settings and directly installed the update IOS 11.1.1. After that I put the back up I made back on my phone.

Did I do this correct?

When I made the back up from infected files, do I put the infected files back on my phone when putting back my back up?