On page 4, there is an "IDE Power" connector. It looks a lot like a 4 pin CPU fan connector, but it (obviously) provides different voltages that are appropriate for 3.5" IDE drives (5V, 12V) and ...

Your picture is of a 20-pin main ATX connector an a 4-pin ATX12V power connector. These do not combine to form the newer 24-pin main ATX connector. That said, many motherboards with a modern 24 ...