ajay babu,
First try to find out the screen exists for ME21N - Create purchase order transaction and create all screen fields in that enhacement screen then only you can able to get it.
The following are the screen enchancements for ME21N
AMPL0001 User subscreen for additional data on AMPL
MM06E005 Customer fields in purchasing document
The above enhancements are useful for you
Goto Smod transaction
-> Give enhacement name
-> press test button
-> double click on the screen number
-> create a screen exist
Regards,
Mahi
