-Just use the information in the 档案. Normally USCIS will not check his previous B-2 visa application materials for his green card application. If USCIS question this issue (if any), then just explain that the parents in his birth certificate were his adopting parents. But don't need to mention that unless USCIS ask. Also need to keep consistent in all the green card application materials based on the information in the 档案.
万分感谢!