going by the photos of the CNC router

To replace the original stepper drivers and breakout board with a G540

you need to find out what motor current the original stepper drivers are set to
very often there is no motor part number or details provided

( you may have to guess and set the current to 2A for example
test the motor when connected to the G540
check the temperature is not over 70C with the axis stepping
note - when the axis is idle the G540 reduces the current
if it gets too hot reduce the current and re test ! )

once you know what the motor current should be
you just need to fit a resistor to each 9 pin plug as described in the Gecko manual
( 1000 ohms per amp upto the maximum or 3500 for 3.5 amps )

more details of the VFD used in the CNC router will be needed
to determin if the VFD can power the G540's PWM to analogue converter
or if you need to add a low power 10 V DC supply

John