This works on my machine. Copy the old configuration files to the new Mach3 directory. The Mach3 directory is usually C:\Mach3 . The configuration files are 'title'.xml . The title is what you called the machine when you created the configuration file. One of mine is bamboo.xml and another mill-a.xml.
There should be an icon on the desktop called Mach3 Loader. Start that program. It should pick up the old xml files and allow you to start them. The xml file contains all the pin information, motor setup, and such, so you should be able to run the machine