If 1 rev of the motor equals 0.1 inch then your steps per unit should be set to 20,000
As for the xml look in your Mach3 folder, if you are using the standard Mill profile look for a file called Mach3Mill.xml Windows may be hiding the file extension from you so it will just look like Mach3Mill, right click on it and choose copy then go to your desktop and paste it there then rename it to shootrock.xml you can then choose the aditional options in the reply page and you can attach it to your post here.
Hood