iPad Pro cellular data

That model number corresponds to a second generation 11" WiFi only 256GB Space Gray iPad Pro.

As such it has no cellular capability, so no actual settings for it would be available.

If you need to add cellular service, you will need to replace the iPad with a cellular capable model, or buy a MiFi device from your chosen cellular carrier.

Are you set up and using a cellular plan on your iPad? Regardless, read this thoroughly.

View or change cellular data settings on iPad (Wi-Fi + Cellular models) - Apple Support

Is your iPad actually a cellular model?

What is the model number in Settings->General->About->Model?