The FasLink has DC 12V output. Pin 1 is negative and Pin 2 is Positive.
if you have DC-DC Converter Module then:
XLR Pin 1 goes to IN- on he Module
XLR Pin 2 goes to IN+ on the Module
and from the Module
OUT- goes to centre of DC Jack
OUT+ goes to Sleeve of DC Jack
That's all. You'll need to adjust the output voltage to 9V on your Module, if you have adjustable one or you could source the one with already fixed 9V output.
There are dozens of the Modules available, Just google DC-DC step-down converter.
For example
DC Jack;
Gikfun DC Power Supply Jack Socket Female Panel Mount Connector 5.5X2.1mm for Arduino (Pack of 10pcs) EK1796
DC-DC Module (I wouldn't go above 500mA) for external supply (this one is too big to be built into an XLR connector):
5PCS 3A DC-DC 3-40V LM2596S LM2596 Adjustable Step-Down Power Supply Module Voltage Regulator