Go to the Vendors Form, Purchase Order tab for the applicable Vendor. Check that the Purchase order prices/amount box is ticked.



This solution did not display the prices for the previous version of the PO confirmation

To solve previous version of the PO confirmation one more trick to sort out the back log issue or previously printed purchase orders ( which will not show the prices any way  even after revising vendor master purchase order default as mentioned ) .

- go to SQL table (VENDPURCHORDERJOUR) select the field AMOUNTPURCHASEORDER

set the value to "1".

For AX 2012

SQL Statement 

UPDATE   VENDPURCHORDERJOUR

SET           AMOUNTPURCHASEORDER = 1

WHERE     (AMOUNTPURCHASEORDER = 0)


For D365
Create Runnable class and use below Code 

   VendPurchOrderJour _VendPurchOrderJour;
 
            ttsbegin;
            update_recordset _VendPurchOrderJour
                setting  
                AmountPurchaseOrder = NoYes::Yes
                where _VendPurchOrderJour.AmountPurchaseOrder == NoYes::No;
            ttscommit;