"NEMA 17" is just a description of the bolt pattern dimensions. There isn't any specification that say what the wire lead connector to the motor needs to be, but they are often a connector make by JST (Japan Solderless connector). They are often referred to just as a JST connector similar to Molex, but that's just the manufacturer, not a specific connector. Your particular stepper may not have 6 pins like that is shown. You could have 4, 6, or 8 pins.
The link provide by Dougal1957 is a possible connector if you have a 6 pin motor with a S6B-PH-K mate. If you scroll down in the table on that page there's a section labeled "Associated Product" that has the pins that are compatible for that connector.
The link provide by Dougal1957 is a possible connector if you have a 6 pin motor with a S6B-PH-K mate. If you scroll down in the table on that page there's a section labeled "Associated Product" that has the pins that are compatible for that connector.