Check required DC motor voltage

I was gifted a couple of DC motors with encoders, and I am not able to get them to spin up. I have only been able to find this ebay page with any information . It list it as 5-24v but when I connect the red to VCC and the black to ground the motor does not spin. Anyway to check what the required voltage is? I do not have an adjustable power supply.

The item you have linked to is not a motor. It's a rotary encoder so it won't move when you apply power.

Russell.