Tom received a firewood delivery, and began stacking it. He noticed that he could stack 3 cords of wood into 4 rows that were 15 feet long and 6 feet high. Each piece of wood is 16 inches long. Next year, Tom wishes to build a wood shed that is 16 feet long and 4 feet high. How many rows of wood will he stack if he orders 6 cords of wood?