I agree with driftrider on the sigh-in height but the magnification of your scope is a personaly preference, i typically have my 3-9 set on 5x even when hunting the big woods here in Saskatchewan. Its a good balance if you are used to it, i have been hunting with this power setting for the better part of a decade is its what i know.

Go with what your comfortable with, snap the rifle to your shoulder and see how fast you can acquire your target and dry-fire as cleanly as possible, try this at various distances, targets and at varying power settings. See what works for you and go from there!

Good Luck!