Since the two bases are regular hexagons, they can be divided into 6 equilateral triangles.
If the height of an equilateral triangle is 3·sqrt(3), its base is 6 and its area = ½·6·3·sqrt(3) = 9·sqrt(3).
Therefore the area of the regular hexagon = 6·9·sqrt(3) = 54·sqrt(3).
Doubling this to get the area of both bases = 108·sqrt(3).
Each side is a rectangle whose area is 6·8 = 48.
For all 6 sides: 6·48 = 288.
Total surface area = 108·sqrt(3) + 288.