You can do the following to find the Princh app on your iPad
The Princh app was primarily built for iPhones, so in order to find the Princh app on an iPad, you must select "Only iPhone" when you search for the Princh app on your iPad.
If that doesn't work, then you can also print from your iPad by going to the webpage print.princh.com on it and manually enter the printer's ID.