You can customize the notifications that let you know about upcoming calendar events, invitations, and more. You can also make sure your events and other calendar information are kept up to date on all your devices.
Go to Settings > [your name] > iCloud, then turn on Calendars.
Note: If you don’t see Calendars, tap Show All to see more options.
If you don’t want to use iCloud for your calendar, you can sync your calendar information between your iPad and your computer. See Sign in and manage your Apple Account on iPad