I purchased more iCloud storage and it is not showing up. What should I do?

It won't show up on your iPad (meaning your iPad local storage will not increase).

Your iCloud storage is in iCloud.

Check iPad's Settings > iCloud > Storage > here

extra iCloud storage DOES NOT add extra internal storage to your iPad.

The only way to get extra storage space for an iPad is to purchase another iPad with larger storage capacitities.