unpaid cellphone account

I have not paid my cellphone account since before the pandemic because this is my U.S. phone and I live in France and could not come to the U.S. I will be going to New York soon and want to use the phone again. I believe the number [EDITED] is still available. I now cannot find my account ID. I cannot sign on online because of that. What should I do online before I leave Paris?

Thank you,

Tom 

[EDITED per Community Guidelines - removed personal information]