You might not be able to cfw that model of ps3 ( I say might because I have a 3xxx myself which used to have 3.55 on it)
If you use minverchk.pup on the ps3 it will give you the factory fw, if that is higher than 3.55 you cant CFW it, only HEN it.
If its lower then your in the same boat as me and don't know what to do yet (see my thread)