I need to design a bandpass filter by cascading passive high pass filter and passive low pass filter
I need to design a bandpass filter by cascading passive high pass
  filter and passive low pass filter


And...


  I have a low pass filter with 3db cut off frequency of 200Hz and a
  high pass passive filter with 3db cut off frequency of 2kHz.


If you cascaded those filters you won't get what you want - the low pass would start to remove frequencies above 200 Hz and the high pass would start to remove frequencies below 2 kHz. In between those two frequencies you would get very little signal i.e. this is a band-reject filter.

If you had a low-pass filter that had a cut-off of 2 kHz cascaded with a high-pass filter that has a cuto-off of 200 Hz, that would work: -