In the Contacts App, update your own contact details in My Card.
Assuming that you are signed-in to iCloud - and you have associated your own contact card with My Card, you’ll see My Card at top left of the Contacts sidebar.
Also, as a point of good practice, ensure that your personal details are kept up-to-date in your AppleID account. Make sure that your contact details include at least one (if not two or more) trusted telephone numbers - and a secondary (recovery) email address that can be used for account recovery purposes.
Should you ever be locked-out of your AppleID, trusted telephone numbers and secondary email addresses are critical to recover access to your account and/or reset your account credentials.
You can update your AppleID from your iPad (or iPhone) settings:
Settings > [Your Name / AppleID] >
- Name, phone numbers, email
- Password & Security
- Payment & Shipping
You can also access your AppleID account using a web-browser:
https://appleid.apple.com