Hi there and welcome
Can you attempt the following please
Go to the Store icon in the menu.
Click on it.
You will be in the iTunes store.
In the iTunes store window, next to three dots (...) you should see a an icon which is the Device icon
Clicking on it will let you select your attached device.
When you do, you should be taken back to the iTunes window where you will see the Summary option at the top of the sidebar.
Then try to restore the backup
Let me know please how you go.