Gas pressure regulators or pressure reducing valves--typically called out in technical drawings as GPRs and PRVs--take the pressure of your incoming gas and reduce the line pressure to an operating pressure suitable for safe operation of the equipment that it feeds.
To size a regulator you need to gather three critical pieces of information: Inlet Pressure, Outlet Pressure & Required Flow Rate. You can find the burners required flow rate and operating pressure on the equipment badge or in the operators manual.