Confusion about Pcie5 and how to power my 4090

So I'm currently attempting to install my 4090 and I was a little confused about how to power it, I had bought a specific PSU MPG A1000G PCIE5 because it was 1000W and something I heard about PCIE5 and how it can power the GPU with only one cable. And so I'm confused which cable I'm supposed to use to power the GPU?

The first cable is the one that came with the GPU, it is a PCIE cable that plugs into the single port on the GPU and branches out into what looks like 3 more PCIE slots to plug cables in.

here's an image: https://imgur.com/gallery/DQYCgfG

The second cable is the one that came with the PSU (which I'm assuming is PCIE5?). It is a singular cable that does not branch out and has 600W written towards the end.

image here: https://imgur.com/gallery/piPv7mF

Which one am I supposed to use? Or do I use them in conjunction?