How to transfer all files from one iCloud account to another
I opened a new iCloud account and would like to transfer all of my data from the current one to the new one.
Photos, keychain, doc, all...
iPhone 14
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.
You can’t merge multiple Apple ID accounts.
See the following Apple articles
Sign in with your Apple ID -> Sign in with your Apple ID - Apple Support
Manage and use your Apple ID -> Manage and use your Apple ID – Apple Support (UK)