How do I change my Porsche Carrera 1999 outside temperature display from Fahrenheit to Celsius?

Bought it in the USA, but shipped it to Poland so I can drive it as my everyday car. Only problem so far is changing the display from Fahrenheit to Celcius. +10 for best answer|||You look in the Owner's Manual. Don't have one? Porsche can get you one, or you can buy them on ebay. This stuff changes, and if I gave you the information from my manual, it might well be wrong (My car is newer and a different model of Porsche).