# How to design a bandpass FIR filter?

I want to design a bandpass filter (BPF) using a FIR filter by the window method.

I have $$f_{c1} = 3\, \mathrm{kHz}$$, $$f_{c2} = 6\, \mathrm{kHz}$$ and slope is $$-80\, \mathrm{dB/dec}$$. How can I find $$f_{s}$$ and order of filter?