Hello I forgot my old iCloud password and now i have different phone number i wnat to change my phone number can halo me

If you forgot the Apple ID password, enter the Apple (iCloud) ID, and click Forgot Password. See if you can get a Rescue or Notification  email option. Link to contact Apple Support at the end of the 2nd article.

Apple ID - Manage            

Apple ID – Forgot Password            

Hi!

Do you have an access to an apple device which the Apple Id is currently signed in?

If yes, try to add the new on Settings > [name] > Password & Security then tap edit next to Trusted number. Once added, try to change the password.

On mac, go to Apple menu > System Preferences > Apple ID. Then, click Password & Security.

If those are not available, you'll need to initiate the account recovery which will take few days.