how can i get my old password so i can change to new password

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

Apple ID - Manage  -     

Apple ID – Forgot Password  *      

Just input your account email to iCloud page, and then follow the instructions to change to your new password without your old one.