Brummie let me explain how CNC machine works regard talking to the Control software (mach3) and things will become more clear.

When you first install Mach3 on your PC it's Dumb as Rock, it knows nothing about the machine. It as no idea it's even connected to the control box.
So you need to Tell Mach3 everything it needs to know so it can talk to the controller/machine.
Now by default Mach3 use's the Parallel port built into the PC to talk the control box and when you installed Mach3 it put a special driver on your PC so it can talk to the Control box if using Parallel port
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However, your machine doesn't use the Parallel port it uses a external USB Card which is built into the control box. So in order to allow Mach3 to talk to it then it needs a special piece of software which mach3 calls Plug-in. Without it Mach3 remains Dumb as a rock and nothing will work.

To get the machine talking to Mach3 correctly is a multi stage process.
#1 Provide with Plug-in so can communicate with control box.
#2 Tell Mach3 which OUTPUT pins control the Motors
#3 Tell Mach3 which INPUT pins to watch for signals like Emergency stop, Limit swithces Etc
#4 Tell Mach3 Which OUTPUT pins to use to control external things like turning Vacuum, cooling etc on
#5 Tell Mach3 which Pins control the Spindle Motor ON/OFF, Speed, etc
#6 Tell Mach3 the Number of Pulses required to travel one revolution and set velocity/acceleration.

So hopefull you can see it's not just install Mach3 and away you go. The simple truth is NO-ONE can help you or show you how to use the machine unless Mach3 as these things in place. The only people who can help are those with same USB Controller and provide you with the Plug-in and settings.
When you have these and mach3 talks to controller any one of us can talk you thru cutting a part in 5mins.

If you can not get the Plug-in then your only option is to replace the USB control card with a different one that does provide Plug-in. (No you cannot use Plug-in from different Card)
That doesn't mean you have to replace the Whole Control box, just the USB card that talks to PC/Mach3. The other settings like Pin numbers can be worked from looking inside the control box. Obviously you will need help either by someone doing it for you or by us helping via you sending pictures and answering questions being asked.
All I can say is don't give up, some one will have the Plug-in or if go the replace route WE can talk you thru this and like WE have done many many times for others.