The board uses a ULN2803 IC (datasheet below)https://www.modmypi.com/download/ULN2803A.pdf
This has a maximum
voltage input of 30V
The stepper motor should just about be manually turn-able using your fingers (they are stiff though).
The 28BYJ-48 stepper included is a 5V board, so you will only need that to operate it.
There's a great guide on using the board here if you haven't come across it yet:http://www.savagehomeautomation.com/pro ... board.html