iPad update

That is indeed a first generation iPad Pro. Which you clearly have not updated in years. That device was released in 2015. So seven years ago.

Since you haven't updated it in years, you'll need to use a computer with iTunes (Windows) or Finder (Mac) to update it at this point.

See these two links:

Update your iPhone, iPad, or iPod touch with iTunes - Apple Support

Update your iPhone, iPad, or iPod touch with the Finder - Apple Support

Have you made sure your particular model iPad is eligible for the update? You have not mentioned which iPad or which update you are trying to get. After making sure it is eligible, check these links...

If your iPhone, iPad, or iPod touch won't update - Apple Support

Updating iOS: common issues and solutions - Apple Community

If yours is an original iPad Pro, it probably cannot be updated beyond its current iOS. It lacks the components needed to run newer software. And you will be unable to use apps that require an update.

Please go to Settings > General > About > Model and report back what exact model you have.

I suspect you don't actually own an iPad Pro. Every iPad Pro model ever sold by Apple is capable of running the current iPadOS 15.5. The fact you have an iPad running iOS 12.1.1 would be a very old device, which is likely not able to be updated past iOS 12.5.5.