I want to change my Apple ID account

What is an Apple ID?

Your Apple ID is the personal account you use with all Apple products and services. It includes the email address and password you use to sign in, as well as the contact, payment, and security details that you use with Apple.

FYI: you can't merge multiple Apple ID accounts.

See this Apple article: Change your Apple ID

Change your Apple ID - Apple Support (SG)

Then see this Apple article: What to do after you change your Apple ID or password

What to do after you change your Apple ID or password - Apple Support