The mating connector to the S11B-ZR is the ZHR-11. They are likely not using all the pins available.
*Note that the ZHR-11 is just a housing and you would install the contacts so you would choose which pins to install/use.
I don't see the reference to the S11B-ZR in the datasheet you linked. It is possible that not all contacts in the 11 way commector are populated1. The datasheet should be clear which contacts are being used.
The S11B-ZR has a 1.5 mm pitch, so a 2.54 or 1.27 mm contra-connector won't fit. You might want to cut off the original connector and solder it to a ...
Assuming torque is proportional to current, we can compute the current as
Current = (1/Inductance) * integral(voltage * time)
Thus MORE voltage for MORE TIME gives more torque.
And Less inductance gives more torque.
There is one number which you need to get: the phase resistance of your windings.
Let's say, as an example, that your windings are 2 ohms each. Then, for a perfect bridge, you would want an 8 volt supply. 8 volts divided by 2 ohms is 4 amps.
Note that this will produce a motor with less torque than specified, especially at high step rates. When voltage is ...
Within the ample insulation rating stated, motors would be damaged by current, not voltage. So within a reasonable range, voltage is just not an issue, so long as the chopping drive does not exceed the rated current.
As already pointed out, the motor drive you want to use does itself have a voltage limit, so you want to stay well within that. This is ...
You should connect one coil across 1A to 1B and one coil across 2A to 2B. The coil will measure as a small resistance on your meter.
Which coil goes to which and the polarity is not too important for your purposes- if the motor turns in the wrong direction just swap A and B of one pair.
You can read in the datasheet that 1A-1B are a pair(motor coil 1), and 2A-2B are a pair (motor coil 2).
So 1A and 1B should go to one coil, and 2A and 2B should go to the other coil.
That means you should probably solder your wires straight. I don't know about the polarity of your stepper motor of course, so it might run the wrong way or something... ...