The easiest way of solving this would be to acknowledge the fact that the base is square. This means that every side will be of the same length.
The way you find the area of a square, is by multiplying the height and width. Since we are talking about a square, that means these values are equal, and therefore squaring. We can find the side lengths by taking the square root of the area.
By taking the square root of 562,500, we find out the side length is 750. Since all four side lengths are equal, we multiply this by 4 to find the perimeter.
We end up with a value of 3,000 feet for the perimeter.
Hope this helped. If you need anything more explained, let me know. The image contains a drawing.