What version of Cubase? Newer versions have ability to change what is viewed in mixer. Actually multiple versions of what you see there.
There should be options under 'Configurations' at top of mixer window if you have a full version. I didn't think limited versions even had input channels in mixer, so likely you just do not have the top menu setup to show it.
Mess with what the mixer displays and you will likely find it. Things have changed recently with Cubase 9/10 and things are different from what I see in your pic.