Where can I find the tables in the buyer work center > Orders?

I want to run a query that looks similar to below : (this is in Purchasing > Buyer work Center> Orders)

But I can't even start my query without the correct tables! I first queried the blanket purchase agreement number using the table name po_headers_all.

I then obtained the po_header_id and used that information to try to get similar results below.

I tried the table names:

po_line_locations_all

po_lines_all

po_requisition_lines_all

po_lines

po_req_distribution_all

I know this is a dumb question and a simple query.... Any help is much appreciated!