As I remember vs As far as I remember

4년 전

  
Do I need to put “as I remember” at the end of the sentence or at the beginning? Why?
Is it a mistake to say, “as I remember” rather than “as far I remember”?
Thank you!
P.S.: I am talking about writing an informal letter for a test.
Dear Anna,
Thanks for your letter. How are you doing? I hope everything’s going well for you. I haven’t been to theatre since college, as I remember.