Thanks for your help!

The website is here. This page confirms that it's an ESRI shapefile, but it also stated that it was compatible with many types of CAD software, so I didn't realize there was a difference. Between the link you posted and a quick Google search, I found a number of ways (including AutoCAD Map 3D) to convert the files, but they all require Windows. Is there a program that is either Mac-compatible or online that will allow me to do the same thing? I even considered downloading a free trial of ArcGIS, but once again, it was only Windows compatible.

Thanks!