I am currently attending RCIA classes and intend to convert to Catholicism. If I want to marry a Catholic in the future, do I need to have my previous marriages annulled since I was not Catholic when I married? If so, is it the same process as for a Catholic, and where should I go to start the process?
Yes, if you as a non-Catholic married a non-Catholic then your marriage is presumed valid. All marriages not prohibited by canon law are presumed valid until proven otherwise. If you married a validly baptized person then you would need an annulment in order to marry again. If you married a non-baptized person then you could apply for either a Pauline or Petrine Privilege (depending on the circumstances).
This process normally begins with your local parish priest.