3x4 is about right, but the original 747 drawings were not drawn on paper, they were inked on thick thermal and humidity stable mylar. Some detail parts may have been defined multiple (up to a half dozen) E sized (36”x48”) mylars. Then there were separate drawings for each assembly of detail parts. Then there was all the manufacturing planning and detailed work instructions to fabricate each level of assembly. Then there is all the documentation associated with lab qualification testing prior to flight. I have personally authorized qual test reports in excess of 3000 pages, where ~100 pages was my content and the rest was all backup data.

The 6 million figure includes fasteners. Half of the parts of fasteners and there are only 75k engineering drawings. Engineering drawings rarely run more than a few pages per part.

https://www.boeing-747.com/fun_facts_from_boeing.php