Hi cindydako,
Welcome to the Apple Community.
Your Apple ID is the one account you use to access Apple services,
like the App Store, Apple Music, iCloud, iMessage, FaceTime, and more.
It includes the email address and password you use to sign in,
as well as the contact, payment, and security details you use across Apple services
You might want to log-in to your Apple ID account online, and see if you need to make the changes there.
Apple support have articles online (links below) that may help.
Update the date of birth associated with your Apple ID
https://support.apple.com/en-au/HT204164
Change your Apple ID
https://support.apple.com/en-au/HT202667
Manage and use your Apple ID
https://support.apple.com/en-au/HT203993
And
If you change your Apple ID or password :
You might need to update your sign-in information with any Apple services that you're using. .
Eg:
What to do after you change your Apple ID or password
https://support.apple.com/en-us/HT204071
If needed:
Here is the iCloud User Guide:
NB: lick on "Table of Contents" at the top of the welcome page that opens from the link, to see topics leading to articles.
https://support.apple.com/en-au/guide/icloud/welcome/icloud
and / oror
iCloud Support Website
https://support.apple.com/icloud
All the best :-)
