To get the information accurately, 20 years ago we would use a video camera with a CMM, or overlay the mylar on a very large optical comparator. You can scan it and then use a raster to vector program if tolerances are not critical.
A lot of old aerospace components with contoured shapes were stored on mylars. 35 years ago I worked at a place that would have the mylar info projected onto specially coated sheet metal to make templates to build up 3D models. Almost everything still flying today has been converted to digital models now.
Iím curious, what kind of info are you trying to get from the mylar?
There are many large curves and radius ,the part not having a straight edge to start from or points to swing these from makes it near impossible to create in my software because I would be guessing on most of it. Is there some way to pick up points with something like a pen, and then bring it in to my cad and then create it. This would save considerable time.
Without seeing what youíre trying copy itís hard do offer any other suggestions. From what I understand so far, it sounds like scanning would be your best option. There are free raster to vector programs available (Google search) that will translate your scanned data into a DXF file that your CAD or CAM program can read.