iPad 3 as recording device - How to Connect Firewire 400 from a PreSonus device Have:
iPad 3 (Apple 30-pin connector)
PreSonus Firestudio (firewire 400 output)

How to connect them?
You don't. Firewire isn't compatible with a full fledged USB controller and the 30 pin connector isn't even a full USB connection to connect peripherals.

Sell the Firewire device and buy a device that will work with the iPad is sadly the best advice I have for you.