From the graph, the coordinates of the longest side are: (-4, 1), (2, 1)
Take the x coordinates since the longest side is horizontal.
The distance will be from -4 to 2 which gives us 6 (on a number line moving from -4 to 2 gives a distance of 6)
Since each unit on the coordinates is 1000 feet, 6 units will be:
6 units * 1000 feet = 6000 feet
ANSWER:
6000 FEET