Pricing is carried out in Purchasing and Sales and Distribution as usual.
You may use the info record in Purchasing for pricing.
If you want the Purchase order price is to be copied into billing document in SD then follow the below Procedure.
You must enter the Price source as A in the path SPRO-Sales & Distribution-Basic Function-Free Goods-Control free goods pricing-Set transfer of costs to main item.
Here for your Intercompany billing type and Delivery type IV and NLCC and for your reference Item category NLC maintain the Price Source as "A" and save.
Now your Price from purchase order will be copied into Billing document provided Purchasing and Sales & Distribution have the same condition type.
You can search in forum as well help.sap.com to get more information in this topic.