transfer Calendar

You would either restore it from the backup of the old iPad, but if you are using iCloud for your calendar, then log into iCloud with the same Apple ID and turn on calendar in iCloud. If you are using a calendar from another email account, after adding that account, turn on calendar.

Okay, so is the calendar still on the iPad? Have you checked with gmail support to see if there is a way to recover that calendar? If the content is still currently on the iPad, Gmail should be able to provide you with method to restore that calendar. Otherwise, if you are not using iCloud for calendars, you should be able to log into iCloud and turn Calendar on, and it should save your current calendar to iCloud.