Why won't this bed's feet touch the floor?
It is a possibility that when the previous owner set it up originally they set it up that way for medical problems, like excess stomach acid.  I've been told by doctors to raise the head of my bed before, but I never did.  He just told me to put wood underneath the feet or wheels at the head of the bed.

If any of the screw holes match up where all the feet rest then try that.  If the wood is not drilled out behind the holes you choose then pre-drill them.