Got these Event monitors... what cords do i need?

Sorry this isn't bass-related.... but i don't know where else to go to get answers...Anyways.. here goes!

I got a lot of recording equipment from my uncle recently... In the bundle of stuff i got, was two Event brand Studio Monitors with a sub. They are the passive monitors....on the back, they have a strange inlet.. i don't know what kinda cord i need to plug em' in .... it's five little pieces of metal stickin out in a star-like shape... i think on the Event website (www.event1.com), they said they were "MDF" cables? anyone know what these are or where i can get em'? i can't find them on musiciansfriend.com or americanmusical.com....

Oh yeah, if anyone knows of a good site like this, just for live sound and recording kinda stuff instead of bass, please let me know...

Thanks so much for your input,
-Evan