iphone restore - new and then use backup
Helping someone with a new iPhone. I wanted to back it up to his iTunes account on his PC, but when I hook up the phone, it goes to a screen that wants to either set it up as "new" or use existing backup, which is dated over a year and a half ago. His phone is backed up to the cloud, and is current, but that is not a screen option. Obviously, I don't want to use an old backup, and I don't want to set it up as "new" without some research. If I "cancel", the iPhone is no longer connected to his iTunes page.
Question - If I set it up as "new", can I then restore it from an iCloud back up? If restored as new, would his iCloud backups be eliminated as well? I don't want him to lose any contacts or other information that would be backed up. He relies on that to remember phone numbers and such.
Help is appreciated.
iPhone 11 Pro