The power steering pump on a BMW 323i (E36 generation, assuming that's what you mean as there have been multiple 323i models) is typically located on the
front of the engine, driven by the crankshaft via a belt. It's often difficult to see precisely without removing some components, but it's generally in the area of the
lower front of the engine, near the alternator and other belts.
To be completely sure, you should consult a repair manual specific to your year and model of BMW 323i. A repair manual will have diagrams and specifics that will pinpoint the location accurately.
