Hi Asim_Ali,
I think the 4210 runs comware 3.
try the command : display device
or maybe you can get it using snmp.
Try OIDs
HH3C-ENTITY-EXT-MIB::hh3cEntityExtManuSerialNum
or
ENTITY-MIB::entPhysicalSerialNum
depending on which MIBs the unit supports.
Regards