With the 3 pp resolver attached to the 3 pp motor, your resolver will now have an electrical angle that is equal to your motor electrical angle. Because they are the same, you should not need to do any conversion between the resolver angle and the motor electrical angle.
I should have clarified my language in the previous post. Your 1 pp resolver has an electrical angle, it just so happens that it is equal to the mechanical angle of the resolver as well (due to a single pole pair). You need to scale the resolver electrical angle with the ratio of motor pole pairs to resolver pole pairs in order to translate into motor electrical angle.
Hope that helps clear things up.