For all practical purposes the current in the signal wires is zero so whatever you have to hand that conveniently fits the connectors will do.

For power to the motor controllers you could Google 'wire current carrying capacity' and find loads of info from a host of different suppliers. Alternatively ordinary mains wire from your local hardware shop should be available with ample rating.

RS Components will sell you a whole host of different multicore cables for the motor wiring but won't tell you the current rating due to a variety f factors which will be explained in many of the results of the above Google search!