Q: How do I determine if I have a generation 3 or 4 Time Capsule?

Click here and look yours up.

(127169)

Alternately, open AirPort Utility on your Mac

Hold down the option key while you double click on the Time Capsule icon

You will see what you have

The Setup Guide below was used for both the 3rd Gen and 4th Gen Time Capsules

Time Capsule Setup Guide - Apple