What EFI Firmware Update should I get?

hi everyone, first thanks for looking into my question,

the situation is that i was out and a trainee did something that blocked the Imac, it stayed frozen for a while, than she cut the power off and tried to restart it; it wouldn't start, instead it makes the folowing vocal message on start :

3 short tones, 3 long tones, 3 short tones,

i looked into it with the help of a friend : here's what we did untill now : we tried to recover the data (crucial...i have so much work on it) we opened it, unplug the HD and he's copying the data now on an external HD.

after i found while browsing forums like this one and the apple assistance that the tones possibly are a message that there's a problem with the EFI firmware, and that if i reinstall it that should do it... but i don't know which one is the right one, and apple website wasn't much of help.

thanks :-)

cheers from morocco