Looking at this Dometic manual at this link on our Owner Empowerment site, I couldn't find any mention of how to change this. Sorry about that. Here's the number to Dometic's Customer Care team: 800-544-4881
Take a picture of the refer name plate (model, serial etc.) as well as the control panel for it.
Contacted Domestic and was advised that my model does not have Celsius degrees, this does not make sense will have to contact the Canadian government to lodge a formal complaint, we are Canadians and do not use the Fahrenheit scale. We buy are rv’s in Canada and expect the metric system.