My MacBook Air says no updates avaiable

I'm unable to updated my MacBook Air software. I've 85GB empty space available.

I tried opening system preferences but there's no software upgrade option available.

I tried doing through App Store but it also says no updates available.

My recent version is macOS Sierra 10.12.6 which is an old version I suppose, that is why it is not supporting few applications.

Please advise what should I Do to upgrade my software.