Verify your Apple ID details -> Sign in to your Apple ID account page and edit / update your Apple ID details.
https://appleid.apple.com
👉 edit / update you trusted phone number, email address & other Apple ID details.
See also -> If you can't connect or sign in to iCloud -> If you can't connect or sign in to iCloud - Apple Support
it says “account locked for security reasons”.
Get a verification code and sign in with two-factor authentication
Get a verification code and sign in with two-factor authentication - Apple Support
See also- > About the 'Trust This Computer' alert on your iPhone, iPad, or iPod touch
About the 'Trust This Computer' alert on your iPhone, iPad, or iPod touch - Apple Support
FYI: 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.
If you stil know your 'old Apple ID', you can check your mail box via another device or sign in online, 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
See this Apple article: If you forgot your Apple ID password
If you forgot your Apple ID password - Apple Support
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