If your iPad has cellular/mobile data support, then it shouldWhilst @Ben's answer is correct for iPads that have a GPS. Please ensure that it's turned onmobile/cellular data connection, and note that tall buildings, bad weather or being inside can affect how it operates.
Now, if your iPad is a Wi-Fi-only model, then you do not have a GPS chip:
WiFi-only iPad models (ones without cellular network capability) do NOT have a built-in GPS.
Source
You may have some luck using an external Bluetooth GPS receiver, however Pokemon Go also requires a network connection, so you will also need to utilise Wi-Fi hotspots or tethering in order to get Pokemon Go to work correctly.