If using CATOS,
"show version" will show Power Suplly Serial Number. Else, use "show sprom powersupply {1 | 2} "
If using IOS, here is the commands to see module information including Part Number and Serial Number
6509# show idprom ?
all selects all FRU-types
backplane specify backplane
clock specify clock
earl specify earl
fan-tray specify fan-tray
interface interface name
module specify module
power-supply specify power-supply
rp specify RP (MSFC)
supervisor specify supervisor
vtt specify VTT
Check this link http://www.cisco.com/en/US/products/hw/switches/ps700/products_tech_note09186a00801c1e9a.shtml