Latin experts: can you help me out? :)

I’m looking for a passive version of the phrase fortēs Fortuna adiuvat, “fortune favours the brave.” I want to know how to turn it into “the brave are favoured”.
I’ve come as far as fortēs adiuvantur, but I suspect fortēs is in accusative case and would have to take on a different form if used as the subject of a passive.

I’d also like to know how to decompose fortēs; is it a stem plus one affix that means plural and accusative?

Context: I intend to use this in my thesis as a concrete example of a language that forms passives in a different way than English does.