itunes won't find update for my phone 6
I want to update my iphone 6 to ios 12 (or at least 10 so I could still use apps). When I try to do so I get notified that I can only update my phone using iTunes. And when I connect my phone to iTunes I click "Check for update" and it says that " This version of the iPhone software (9.2) is the current version" . What does it even mean? Please can you help me to update somehow to even ios 10 because I cant't use more than half of the apps because of the old software. Thank you.
iPhone 6, iOS 9