How should I power a 3V toy motor?
Yes, supply approximately 3 V. (If you were to use higher voltage, you might need additional current limitation to avoid burning out the motor.)

You can connect AAA in series to add up the voltages, for example using a battery holder like https://www.sparkfun.com/products/14219 with a built-in switch:



You can also move up to AA for longer running time. There are many variants of battery holders available.

You will need basic soldering skills and it doesn't hurt to buy a cheap multimeter. I'd say you're running minimal risks with so low voltages. A 9 V battery will sting if you put your tongue to the terminals but that's pretty much it. Oh, and most people burn themselves on a solder iron once before learning to show proper care. You might be able to wrap the stripped wire ends on the motor terminals to avoid the soldering.

Have fun! :-)