Hi Abhishek,
U can use report program for this.
I will try to explain you the basic tables and key fields that you will need to require to develop your logic.
Tables required will be : EKKO,(PO header) EKPO (PO line item) EBAN (PR requisition).
Get the PR number EBAN--BANFN from the PR table.
Pass BANFN-EKPO to fetch EBELN.
Pass EBELN-EKKO to create the PO.
Revert for further queries,Else award answer as useful.
Thanks,
Kishan