How to find account #

I have had my prepaid Iphone SE for 3 years or so and I am trying to transfer my current number over to a new phone. I don't have my account number on hand and i cannot find it anywhere on the prepaid at&t site even after i logged it to my account (using my cell number). I need the account number to transfer my current phone number to my new phone. Any help or ideas would be greatly appreciated.