Required number of fans are already installed in the server as per the photos & the part number on the parts:
667254-001Fan module assembly - 92mm x 92mm (3.62 inches x 3.62 inches) - Includes latch - Three used with single processor, four used with redundant fan configuration or dual processors
The fans get connected to the System Board (Mother Board) directly. The AIR will be blown out from the rear with help of the Air Baffle.
Hence, you just have to install the CPU's & the Heat Sinks. Keep the Fans as a spare.
Thank you