I tried to apply but it’s asking for last four of my ssn when I enter it says not the right ssn for the account holder?

Where do I find my information for my account within Apple Store? I tried to make a purchase and that’s the last four of my Social Security number when I entered them and say it was the wrong numbers for the account holder? I was unaware that I even had an account or information within Apple Store as I have never been purchased before where do I find this information?