Look at the motor stator and count how many " fingers " it has. That is the number of poles. Example, the motor pictured has 12 poles. Unless you have a programmable ESC that has you select the number of poles it really is not much of any real concern, all it does is give you an accurate rpm readout if you have an ESC with telemetry or can plug in a programmer with RPM readout. Timing is a more critical aspect, most of the cheap ESC's will just have a timing selection of inrunner or outrunner. An inrunner requires timing from 0 to 10 degrees, an outrunner 15 to 25 degrees. When you hear the dreaded motor screech it's because the ESC timing is off and the ESC has lost sync with the motor. Quite common with the higher pole count motors such as the Hacker 28 pole Q80 motors. Typically the higher number of poles requires the more advanced timing. Motor diameter plays a part in this as well. Since operating firmware for each ESC brand is a bit differnt, settings from one brand of ESC don't laterally match up with a different brand. Some trial and error is required to reach optimal settings. This will change some depending on battery performance and prop size as well.