I like to find what apps are compatible with the IPad IOS 5.1.1

At this point probably none honestly. An iPad that cannot update beyond iOS 5 is an original first generation iPad and is at this point 10 years old

But you can look in the App Store directly on the iPad, and look for iOS 5 compatibility. All apps list their iOS version requirements in their details section.

There is no actual list of iOS 5 apps you can access.

At this this very late date, more than likely, none.

If this iPad is new to you and has been reset, getting apps for that iPad, now, initially, from the iOS App Store, will, more than likely be a futile effort.

Especially so for ANY popular apps.

The 1st gen, 2010 iPad will be 10-years old in April, 2020.

This iPad was an “early adopter” iPad and Apple ended its support for this iPad after ONLY one year!

Third party app developers, basically, ended support for this iPad back in 2015/2016 with Apple's transition to all 64-bit hardware/software.