Help me update date my psp to ver 6.31?

ok i have a psp 2001 it is the sliver one i have sof wear version 5.00 m33 6 i downloaded the sofe wear from the playstation store but i try to put it on and it says cruopt data can some one tell me step by step on how to do it i am trying to put version 6.31 it is a PBP file do i need to change it into some thing esle for it to read plz i am stuck