Where can I find the SIP account credentials for my fritzbox?

Hi! Is there a way to get the SIP account credentials in order to manually set up a fritzbox? I just moved, my number got changed but I can not register the new number in the fritzbox because I do not know the new username and password for this SIP. The old number strangely is still active on port 1 and I was instructed to use port 2 for new number but no creds were provided in the email.