3D AutoCad Strings as Point Control

I asked this question previously but it was flagged as inappropriate.  I then got an e-mail supposedly providing a link to a form to appeal that classification, but the link took me to a blank page where I could make no such appeal.  This is not a great introduction to this "community".  I'll ask my question again.

I have an AutoCAD dwg file with 3D strings in it that define the edge of a bridge deck horizontally and vertically.  I cannot however select these strings to use as point control for the edge of the bridge deck in OpenBridge Modeler.  What do I need to do to be able to utilize these 3D strings to define the edge of my bridge deck?