Using an unipolar 6-pin stepper in bipolar 4-pin mode is always possible. You just have to find out which pins are the center tabs and leave them unconnected. For this you best measure with a multimeter the resistance between the pins. This should give you 2 groups of three interconnected pins. Within a group you have to leave unconnected the pin which shows the same (lower) resistance to both other pins and connect the two pins which between the highest resistance between them to you controller board.
It remains to see though, whether the motors are strong enough... I have successfully used similar motors for the Z-axis.
It remains to see though, whether the motors are strong enough... I have successfully used similar motors for the Z-axis.