INCONVENIENCED PAY MY DOCTOR: WHERE'S MY CLIENT ID?

Okay, so, I need to cover my doctor's invoice. I went the portal and it says I need a account number. However, I can't that! What am I supposed to check? Is there a way to retrieve my client ID? Help me figure this out. It's really annoying having to halt payment because of this. Veradigm & Pay My Doctor: A Guide Navigating your medical costs ca