In that case, you have a licence for life I believe. You just need to revalidate your Class Rating.
This page seems to cover it:
You'll probably also want to consider converting to an EASA licence (this used to be just a paperwork exercise, I'm not sure about the procedure now).
Note, I am note an Instructor or Examiner, so don't take what I say as read. A lot more knowledgeable people hang out at the other Internet Forum, so you may get more authoritative answers there.