In a shoplifting incident, in 1985 when filling out paperwork - do I list it as a conviction.

You need to know how the case was resolved before you can properly answer the question. Go to the County Clerk's office for the County where you were charged. Call or go in person and ask them how to get a copy of your criminal background. When you get it, see whether it was in fact a successfully completed deferred probation. An adjudication would mean that you did not successfully complete the deferred probation. If you were adjudicated, then you have a conviction. If you successfully completed the deferred probation, then you do not have a conviction.