-- The building sits on (60 x 50) = 3,000 square feet.
-- The parking lot, occupying the rest of the square plot, is 16,600 square feet.
-- The total real estate is (3,000 + 16,600) = 19,600 square feet.
You said that the plot is a square. That's valuable information. Without
knowing that factoid, we wouldn't be able to calculate the dimensions, even
knowing the area.
-- The area is (length) x (width). The length and width of a square are
the same number, so the area is (length or width)², and the length and
width are both √(area).
Length = Width = √(19,600 square feet) = 140 feet .