To make this clear, because your English is messed. This is what you have right?:
The black, is the PCI-e connector, that would go to the graphic card. The two white connectors, that you call "flat plugs", are called 4-pin molexes. Those connect to, two 4-pin molexes, coming from the PSU.
The black, is the PCI-e connector, that would go to the graphic card. The two white connectors, that you call "flat plugs", are called 4-pin molexes. Those connect to, two 4-pin molexes, coming from the PSU.