How can I display GPS coordinates on my ipad with wifi+cellular and ios 12.14

Use the Maps app. If not enabled, enable Location Services generally and also specifically for Maps by navigating to Settings > Privacy > Location Services. For your current location, in Maps tap the Current Location button (arrowhead icon) in the upper right. Tap your current location (blue pulsating dot). For any other location long press until a pin icon appears. Read the latitude and longitude in the panel to the left.

in iphones the compass app does it

but not sure if it's in ipads so you can get a free one ‎Compass for iPad (Free) on the App Store

the google map app also has it

As Roote says, just use the iOS Apple Maps app.