It should be labeled Command/CMD/

/or have a weird little gear kind of icon and should be the first key to the left of the space bar.
You can also try to reset the SMC if the PRAM/NVRAM reset does not work:
1. Shut down the computer if not already off.
2. Plug in the MagSafe power adapter to a power source, connecting it to the Mac if its not already connected.
3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time.
4. Release all the keys and the power button at the same time.
5. Press the power button to turn on the computer.
Note: The LED on the MagSafe power adapter may change states or temporarily turn off when you reset the SMC.