Distance is measured in feet (or other linear measurement) and area in square feet (or other measure of area. Linear measurements have one dimension and area measurements have two, so you can't compare them or convert one into the other. A line doesn't enclose anything, because it's just a line. An area is an enclosure like a circle, rectangle, triangle, square, and so on. To make an area out of a line you would have to bend it and join the ends together.
The best we can do with the figures in the question is to bend a line to make a shape. Let's go for a 45 degree right-angled triangle. The area of this type of triangle is half the area of a square split into half along a diagonal, and the area of a square is the square of the length of the side, so the area of the triangle is half this value. Now look at the figures representing the area of the triangle. To find the area of the square we simply double the values: 1600, 3600 and 2500. The sides of the corresponding squares would be 40, 60 and 50 (40*40=1600, 60*60=3600 and 50*50=2500). So we know that the sides of each triangle forming the right angle must be 40, 60 or 50. The length of the third side of the triangle is the length of the diagonal of the square and would have respective lengths 56.57ft, 84.85ft and 70.71ft. The length of the lines forming these triangles would therefore be 136.57ft, 204.85ft and 170.71ft. These are the perimeter lengths of the triangles.
So now I hope you can see the difference between feet and square feet. We could have bent our line into a circle and the line would be the circumference of the circle and the answers would be quite different. Or we could have made another shape, all giving different lengths for the lines making the shape.