How many pieces of paper would it take to cover a football field?

One hundred thousand

8 1/2" * 11" = 93,5 square inches = 0,649305556 square feet per sheet of paper.

A foot ball field (including end zones) is 120 yards * 60 yards = 7200 square yards = 64800 square feet.

64800 / 0,6493 = 99798

almost 100 000 sheets of paper.