How do you write a letter to the principal of your college requesting for transfer of class?

As i have studied in your university on 1990 "B.A.(HISTORY)" in correspondence but i attended the exam first semester only, and so further i cannot continue my studies due to some reasons and now for my sons future education they are asking my 12th transfer certificate . So i kindly request you to give me my 12th transfer certificate (or)B.A. discontinued certificate as soon as possible.