How to Transfer movies from computer hard drive to external hard drive

I have hooked up an Iomega HHD1H UltraMax 500Gb External Hard Drive using a FireWire800/FireWire400. What I want to do in order to save 'computer' hard drive storage space is to transfer most of my 'stored' HD movies (including many in 1080p) from my computer's HD to the external Iomega Hard Drive and then be able to play them back at leisure on my MacBook Pro.

I originally used the Iomega and another one as external storage of movies when I had DishNetwork. Now what was recorded then is still on the Iomega's but I don't know if it is recoverable to view on my MacBook Pro. If not, how to erase?

Thanks in advance for any help.

Michel