Question marked as
You are sign in here . . . with your Apple ID & Password (?).
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.
Check your Apple ID via your email box, see this Apple article: If you forgot your Apple ID
If you forgot your Apple ID email address or phone number - Apple Support
OR see -> Having trouble signing in?
https://iforgot.apple.com/password/verify/appleid
If you've forgotten your Apple ID email address or phone number
If you've forgotten your Apple ID email address or phone number – Apple Support (UK)
See also -> If you can't connect or sign in to iCloud
If you can't connect or sign in to iCloud - Apple Support
Sign in to your Apple ID account page and check your Apple ID details.
-> check your trusted phone number.
See also -> Use your mobile phone number as your Apple ID
Use your mobile phone number as your Apple ID - Apple Support