So the proper way to set it up is:
CMCalibratedMagneticField magfield = motion.magneticField;
//send in the magfield to the function.
In my code I was indirectly trying to reference the value on the function side of this code and so was unable to get any direct values from it. But my function call now looks like:
-(void)showMagneticfield:(CMCalibratedMagneticField)magfield
and then calling the various fields by doing magfield.field.(axis)