Finding Coupling Coefficient between two resonators

Hello everybody,
I have a question about cavity filter design, I?m new in the RF Filters,
while finding the coupling coefficient between two resonators I?m using eigenmode solver in CST but I dont know what does the modes mean? which mode should I choose in eigenmode solver ? and my cavity filter design consists of 6 cavities how to calculate the rest of coupling coefficients between cavities (eg.3th,4th,5th,6th cavities)

Thank you for your help?