I'm getting a bit out of my depth here, Musicmummy, but I'm guessing you need the information from your router, not from your PC. If so, you need to go into your router's settings in order to find the information you require.
Now you're probably going to ask me how to access your router settings. That's where things might get a bit tricky!
Your router should have come with a manual. It might be a paper document but it's more likely to be a PDF (or HTML) file which is either on the CD which came with the router or was put onto your PC when you installed the router. The manual should tell you how to access your router settings.
My router settings are accessed via a local web page. I enter 192.168.2.1 into the address bar of my browser, and then click 'Go'. (That takes me to a login page). My router is from Belkin. If you've got the same make, the same URL should work. However different makes of router require a different address to be entered into the browser. If you can't find the manual (which should tell you how to access the settings), try googling the name of your router, together with 'settings'. Alternatively, post again and I'll see if I can find the relevant information.
Chris