FireWire 800/400 9 pin to 6 pin instead of FireWire 400 to 400?

Hello! Still trying to figure out my Mac. Need assistance. I bought a LaCie external hard drive for my MacBook since I have a model foam 2008 (the one with the removable battery). Need space on my MacBook bad. 3 GB left on drive. Since I am still a newbe I put it off as long as I could because I don't understand what to do.

The guy at best buy was a Mac guy and he said I needed a $30 FireWire 800/400 9 pin to 6 pin cable. But when I opened up the drive to finally do it last night there were 2 cables included one 800 to 800 and one 400 to 400. My MacBook has the 400 slot.

Do I need the 800/400 9 pin to 6 pin cable? Would it increase the speed over the 400 to 400 cable included with the drive?

Thanks for any help. I feel so overwhelmed attempting this by myself.

Thanks for the quick reply!

Thanks so much!

Crud. I waited till it was too late to take the cable back to even to attempt this. I am a terrible procasternater when it comes to the upkeep of my own stuff. I need to transfer iTunes off my Mac onto the external drive to have space to do anything with it. Since I wasn't confident on how to do it, I keep putting it off.

Thanks so much for your help!