Trying to restore new phone from itunes back-up but say iTunes out of date?

Instructions for updating iTunes.

Mac

1. Open iTunes.
2. From the menu bar at the top of your computer screen, choose iTunes > Check for Updates.
3. Follow the prompts to install the latest version.

Windows

1. Open iTunes.
2. From the menu bar at the top of the iTunes window, choose Help > Check for Updates. Learn what to do if you can’t see the menu bar.
3. Follow the prompts to install the latest version.

Get the latest version of iTunes - Apple Support