First, let's determine the volume of the layer of topsoil. That would be equal to the product of the dimensions of the garden, times the height of the layer of soil. To maintain consistency of units, 2 inches is equal to 1/6 ft
Volume = (27 ft)(32 ft)(1/6 ft) = 144 ft³
Also, 1 yard is equal to 3 feet. So, the equivalent volume in cubic yards is
Volume = 144 ft³ (1 yard/3 ft)³ = 16/3 yd³
Amount of cubic yards = 16/3 yd³/1/4 yd³ = 21 1/3
Thus, you would need to buy 21 and 1/3 of 1/4 cubic yards so that it will have a total volume of 16/3 or 5.33 cubic yards.