How do I verify that this is the replacement operator I need

I would first start by removing one of your existing operators from the window. Then, measure you operator and match up those measurements to the dimensions found in the 39-216 & 39-217 product picture.

If you need a dimension that is not listed, or an alternate view of the operator you can make that request here in this discussion.

If you need help take a few pictures of your operator removed from the window and submit your images here for us to review. We may be able to determine what you need based on your pictures.