From the Navbox website:
GPX export - The latest version of ProPlan ( 5.40 ) includes an option to export a route in the popular GPX format. This format is supported by, amongst others, the Garmin AERA series. To use this function with the AERA series you will need to place a micro-SD card in the GPS card slot ( in the battery compartment of the AERA series). To use the export module you must have ProPlan version 5.40 or higher.