Version of Airport Extreme

Hi All. I just purchased an AirPort Extreme Base Station today. I ran down and picked it up from Best Buy, with the understanding that I can set up a guest network. When I navigate to the Wireless tab within the AirPort Utility though, there is no option to set up a guest network. After some research, I understand this option may be hidden if the modem I am using is not compatible. I just want to make sure that this is the reason for this and I didn't buy an AirPort Extreme that had been sitting at Best Buy for years (old model). Does anyone know how to tell if I did purchase the latest edition of the AirPort Extreme? On the bottom sticker, it has the following:
MD031LL/A Model No. A1408

I'm not sure if this means anything to anyone, but any help/advice would be much appreciated. Thanks!

I don't see that. Here is a shot of what mine looks like:

I am running the latest version:
6.1 (610.31)

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I am partially there. Under the Network tab is the Router Mode setting. This was set to "Off (Bridge Mode)". I changed this to "DHCP and NAT". Once it updated, I now have the guest network option. Although I'm not exactly sure what the differences are between these options, and the light on the router is now blinking amber color.

Yep; I actually figured it out last night. Under some Advanced area within the Admin area of the modem/router combo, I found a Routing and NAT setting. I disabled this, unplugged/replugged the modem/router. After that, I was able to do Routing and NAT on the AirPort Extreme and everything worked just fine.