Size of Impeller Wheel

I recently purchased a reef tank setup. The system is 180 DT with a 75 sump. The impeller wheel for the Reef Octopus skimmer is cracked (found upon cleaning). I am unsure what size simmer I have? I believe it's a NWB version as it is all black and going in the sump. How can I tell which replacement wheel I should order? Also how long does it take to ship to Wisconsin 54901?

Thank you,

Brian Bachem