It sounds like you might have a misconception about counter tasks. It isn't necessary to have a very high sample rate when measuring frequency. In fact, high sample rates lead to larger quantization error effects.
In any event, your 9411 module is mainly a pass-through interface for your digital signals. The cDAQ chassis contains the clocks and timing engines used for sampling. Look up manuals and docs for your particular chassis to see what methods it supports for frequency measurement and get a better understanding of how they work.
FWIW, when I was doing similar measurements, I most typically used the method called "Low Frequency with 1 Counter".
-Kevin P
CAUTION! New LabVIEW adopters -- it's too late for me, but you *can* save yourself. The new subscription policy for LabVIEW puts NI's hand in your wallet for the rest of your working life. Are you sure you're *that* dedicated to LabVIEW? (Summary of my reasons in this post, part of a voluminous thread of mostly complaints starting here).
