Hoping someone might be able to help with this one.
I’ve built a Primo and currently running marlin on it. I want to change to grbl and thought I would move from 4 independent steppers to running them in pairs. (less faffing about in the config).
So I purchased some parallel stepper modules from Amazon, not realising that wiring in series is the preferred option out of the 2.
So on to my question: can I still use the modules, but just change the wires around to match the series connections?
Maybe include a link to the modules yoou purchased, or else we’re just guessing… If they are just 4 pin connectors with some wiring, probably, but without knowing what you purchased, it’s difficult to say.
Using a parallel adapter board to connect motors in series is going to be a mess with wires from both motors going to one connector etc. I’d avoid that TBH. Maybe you can return that to Amazon and order a series adapter instead?
Yeah, it would help wouldn’t it! 
These are the ones I bought: 5pcs Dual Z Stepper Motors Parallels Modules with 100mm Cable for 3D Printer Parts Accessories https://amzn.eu/d/7fbt8TN
It’s probably not possible to use those and get a serial connection without just not using one of the parallel connections on the board (in which case you should just not use it as it’s just additional connectors that could come loose). The wires are probably fine to do in series, just the PCB module is probably not helpful for you.
You will find the series wiring diagram on this page. You could make this connection work by cutting all the traces on the back side of the board and then bridging some wires between the connectors to match the diagram. Beyond what Rayan used to sell, I’ve never seen a series cable/connector. I sure they are sold somewhere, but they are not common, so you will likely be rolling your own in some fashion.
The description there says serial and parallel. It also says the current is split. That’s ok. We sort of made up the terminology. Test them first to see if they are parallel or serial (the easiest is to just plug in one motor, the serial adapter needs both for either to move).
If those don’t work, you can build a similar thing with the diagram Robert posted. NBD.
We used parallel on our machines for a long time (but doubled the current at the steppers). We used serial for a long time too (some of us still do). Not getting individual drivers is not a big deal.
Hope this helps…
Wait, wrong forum…
Thanks for the replies guys.
I’ve knocked together a couple Y cables to run the steppers in series as per the advice given. Plugged them in and we are alive. Dodgy connection on one of the wires, but sorted that now.
Never thought to test the modules, gonna give that a go now.
Thanks again everyone.