You've got a great recipe that gives the oven temperature in degrees Centigrade (°C) or Fahrenheit (°F) but you have a gas oven which uses gas marks. So, here they all are for you.
The oven setting above are only approximate as individual cookers may vary slightly. Gas oven regulators are not absolutely accurate, so you can't guarantee that the temperature will match the gasmark exactly. This shouldn't be a problem with new gas cookers, but older cookers may be less accurate.