Garmin Nuvi software - convert to google earth format?

Hi all
Been OS so not on EO for a while. Hired a car while away (Diesel Hilux 3l D4D, 12 seater high roof) – beaut beast. Did 3300km. Hire company threw in a Garmin Nuvi (not sure the model – probably 2 years old or so). I managed to download its entire file structure. Would like to generate a track file – preferably in Google earth format (.kmz file) to plot where we went. How do I do this?

Alternatively, is there someone with the software that could convert it for me – if so what file type contains the track info.?

Cheers