The xml and licence will be in your Mach3 folder on your computer, if it was installed to the default location it will be C:\Mach3
The xml will have the name of the profile you are using, for example if you use the default Mill profile it will be called Mach3Mill.xml, if you use a custom profile it will have the name of that custom profile with a .xml extension.
Licence file is called Mach1Lic.dat
Hood