Will the USB adapter to 25 pin work to run Mach 3 or will I need to have a 25 pin port put on my computer
You must have a parallel port. If you don't have one then get a PCIE one for your computer. The usb protocol messes up the timing so the standard usb to parallel adapter won't work. There are some usb solutions but they do all of the processing on board and they are very expensive. Good luck.