If you got a wire, there would have to be an option to plug it straight into the motherboard from that connection on the case (check the motherboard manual).
As for the plug in card if there is no connection on the motherboard, it is best to go on the internet for a trusted shop, and just look for 'Firewire add on cards' or even 'Firewire' in the search.
Same thing would go for the wires, but these would be much cheaper than a whole add on card if your motherboard supports it straight off, but you said it doesn't.
These cards should then plug into a spare PCI port on the motherboard and work straight away. The one on the case would not have to matter