I'm struggling to find the name of a connector I just broke, so I can order a new one.
It's a six pin nylon terminal, that plugs into a set of header pins on a stepper motor.
What do I search for to find these?! Also, how would I go about finding something like this in the future? I seem to struggle to find connectors.
Short answer: It's probably 6 pin JST PH
Long answer:
Without seeing the socket, it's hard to say for sure, however most Nema 17 stepper motors use 6 pin JST PH connectors with 2.0mm pitch on the motor side. Many control boards use JST XH connectors with 2.5mm pitch on the board side. The two are not compatible with each other due to a difference in pitch and the locking mechanism.
Looking at the sockets there is a clear visual difference: PH has a wide cutout while XH has two slots.
PH vs XH
The difference on the plug side is more subtle. XH has small hooks that grab onto the slots while PH has not.
There's a good reference at mattmillan.com which helps to identify different types of JST connectors.
EDIT: Usually the easiest and the cheapest option is to buy a pre-made stepper motor cable that fits your control board. However if it's not available in a length you need or re-wiring is hard, you will need connectors and a crimp tool with jaws specifically made for these types of connectors. The cheapest option is probably to borrow one if you can, these can cost a pretty penny.
Answering the second part of your question is tricky. Searching through parts catalogs is too time consuming. Using google image search or google lens to search with images taken from multiple angles is a good start to narrow it down but does not guarantee success.
In an attempt to salvage my (sadly) previously incorrect answer (at the bottom), and to add to anttix's superlative answer, here is a quote from Stepper cable for MKS Boards pinout, which clearly shows the difference - locking and non-locking, and pitch difference (note the thickness of the plastic between each individual pin socket) - in the two plugs:
This pinout information will help you to use our 1 meter stepper cables correctly. Cable was made to be compatible with 6-pin JST connectors on NEMA 17 stepper on one side and 4-pin JST connector on other side. These cables are compatible with MKS BASE and MKS Gen boards that we sell in our store.
For compatibility with Anet board you will need to swap 2 wires - RED and BLUE on the 4 pin board side connector.
Whilst they aren't labeled PH and XH, it is pretty safe to assume that:
The mattmillan.com link in anttix's answer, whilst informative, unfortunately doesn't show both sides of the 4 or 6 pin connector.
For the sake of completeness, but at the risk of going off-topic, the connector to the printer controller board is often a DuPont, and not a JST, particularly in, but not limited to, Arduino (Atmel/AVR based) boards.
From the same website, this page Stepper cable for RAMPS pinout, shows the DuPont connector to the control board and the JST-PH-6P connector to the stepper motor (I've not fixed the typos in the quoted text):
This pinout information will help you to use our 1 meter stepper cables correctly. Cable was made to be compatible with 6-pin JST connectors on NEMA 17 stepper on one side and RAMPS board connector (also called dupont connector) on other side. Main feature of RAMPS stepper header and this cable is that you can reverse stepper direction by turning connector on RAMPS 180 degree.
This cable is aslo compatible with CNC V3 shields for Arduino UNO and other electronic boards for 3D Printers and CNC control. Please observe the following piut diagram to make sure that your particular electronic board is compatible.
Note: I'm not promoting this particular website, it just so happens that they have the best comparison photos.
Maybe It is most likely not... JST XH 2.54 6 pin female
and the reverse side, showing the locking, with the male PCB connector
