When you turn your new mac on (do you mean macbook pro, and not powerbook? there hasn't been a new powerbook in over a year....), it'll tell you about migration assistant.
it'll ask if you want to transfer data from an old mac, and tell you what to do.
(basically, connecting a FW cable as mattie says.)
however, my point is that i'd let the migration assistant do everything, and not use target disk mode unless you need to.