I don't think there is any way to directly convert as you are wishing. There are quite a few aspects of a prop that affect its performance; blade shape and width, thickness, helical pitch, flat or under cambered, tips square or round, what engine...... Given what little you really have to start with I guess I would start with 10" diameter since I'm adding a blade then use about the same design and pitch you have now. It will still be a completely different prop but in carbon you will heat and re-pitch the blades anyway if its not on the money. Make a number of them so you can modify the tips, etc., to experiment.
Dave