Q: 3 pin firewire cable converter

Firewire adapters come in all shapes and sizes.  Amazon is a good place to look at possibilities based on the two ends you have to connect - I suspect you need something like this example (standard disclaimer applies: I'm not advocating you purchase from Amazon specifically):

http://ecx.images-amazon.com/images/I/71xB21cPMxL._SL1500_.jpg

But once you have it electrically connected to your Dell, you may or may not have the software (and OS) capability to drive it... that will depend on the app you want to use it with.