Instead of a prescribed change interval, Ford recommends having the transmission fluid and filter inspected by a qualified mechanic during routine servicing. The mechanic will assess the fluid's condition (color, smell, presence of debris) to determine if a flush or replacement is necessary. Severe driving conditions (towing, frequent stop-and-go traffic) might necessitate more frequent checks.
Therefore, there's no definitive answer like "every 30,000 miles." Consult your owner's manual for the specific recommendations and follow your mechanic's advice based on the condition of your transmission fluid.
