150 ft * 160 ft = 24 000 square feet. 4 000 sq feet of lawn requires one pound of seeds so 24 000 sq ft of lawn will require 6 pounds of seed.
Go to the store, determine what kind of grass you want, read the information on the package and it will tell you how many square feet the bag will cover.
That is impossible to anwer. An area cannot be converted to a weight, mass or force.
I am almost certain area cannot be converted to a weight or vice versa
Weight and area units cannot be interconverted; there is no way to compare the two, even by using another property such as density.