What if I got a new number and I forgot that my old number was connected to my iCloud ? How do I get my iCloud back ?

Why are you having trouble accessing your iCloud account? If you forgot your password, see if you can get an email option. If it isn't a password problem, do you need a verification code?

Enter the Apple (iCloud) ID and click Forgot Password.

Apple ID - Manage            

Apple ID – Forgot Password            

See if anything here helps.  If necessary, you can use account recovery as explained in the link at bottom of the article.

Verification code - how to get one and sign in with two-factor authentication.   

Try changing the phone number of your trusted iPhone in Apple ID Account  Apple ID Account https://appleid.apple.com/#!&page=signin. Before making the change, sign out of Messages/FaceTime on all our devices. And, note that the change will take up to 24 hours to take effect.