"N600" is a speed, not a model number. Look for "Model" on the product label. Firmware version? Connected to what?
> Where do I find a pre shared key for my router
What are you doing? What generated this question? Do you mean the wireless-network passphrase, or what?
Guessing, based on approximately no useful information:
Visit http://netgear.com/support , put in your (actual) model number, and look for Documentation. Get the User Manual. Read. Look for a topic like "Specify Basic WiFi Settings". Further reading might not hurt, either.
