ok, my suggestion is to get a 5V power supply, connect this to the positive side of the pul+, DIR+ and ENA+.
Then the step goes to the PUL-, direction goes to DIR- and Enable goes to ENA-.
This bob is very simble and has no opto isolation of buffering and you are reliying of the quality of the 5V from the parallel port.
In most cases it will be under spec and 3V is borderling working or not, and any noise will give you problems.
you could also use the 5V from the USB, but i would not trust that, so getting a 5V power supply is much better.