Shooting out to 500 yards,a 3x9 isn't gonna cut it.
I have shot deer and pronghorn at just under 500 yards with a 3x9.I currently use 3x10s and find them plenty for big game hunting to 500 yards.
What you need to do now is budget for the ammunition that you will need to shoot out to 500 yards with that rifle to learn the actual trajectory and windage out to 500 yards,as well as develop your shooting skills to become proficient at 500 yards.You won't accomplish that with two or three boxes of ammunition.