"Frenchs" is impossible in a couple of ways. First, you would have to spell it "Frenches". Second, it is not an English word; your options within the language are "Frenchmen" or "the French".
"Chinaman" is considered racist now, but I suspect "Frenchman" is still good.
"Chinaman" is considered racist now, but I suspect "Frenchman" is still good.