If the prosecuting attorney doesn't object to the motion to set aside conviction will there be a hearing?

Did you file a motion yourself? If that is the case, it is time for you to at least speak with a few attorneys locally.

Assuming you have properly filed your motion, affidavit and order and your are properly eligible for expungement-- if the DA does not object, there will be no hearing and your expungement should be granted.

In Portland if the DA does not object (they will send you a notice and proposed order) then there will not be a hearing. If the Da objects to your motion they will send you a letter outlining their objection; then it is up to you to either withdraw your motion, contact the DA's office within 30 days to request a hearing, or do nothing (in which case your motion will be denied).