Should be this one:
In case you're on Illustrator CS5 (or lower) and Windows, see this as well:
There's an English description here: http://www.ika.ethz.ch/plugins/publi/pdf/2006_werner_hutzler.pdf
Hi - you might want to check out the forum CartoTalk at http://cartotalk.com
There are open source GIS software, like QGIS (if you are on a tight budget) that can export to files that you can use in Illustrator. But you might want to consider contracting a GIS professional to prepare the data for you.