Adding RTX 4090 graphics card to Precision 3660

I have a Dell Precision 3660 and I bought an MSI GeForce RTX 4090 Suprim Liquid X 24G becuase it only takes 2 PCI slots. Last week I sent back a ZOTAC Graphics Card ZT-D40900M-10S 24GB GDDR6X NVIDIA GeForce RTX 4090 because it takes up 3.5 slots and my Dell only has 3 slots free. I can fit the new MSI card in and its fan/radiator assembly (by removing the existing fans and the hard drive cage, which I don't use) My problem now is that the connectors from my 1000W PSU don't match the power connectors for the graphics card. The card has 4 x 8 pin connectors and the PSU gives me two power lines. Each has a 6 pin connector, one also has an 8 pin connector and the other has a 6+2 pin connector. MY computer is only 18 months old and cost me €6,500 so I really don't want to have to replace it but I need the RTX 4090 to do massively parallel computing with the GPU. It will speed up my calculations by a 4x factor. (I bought an RTX A4000 when I got the PC)

My PSU has these connectors:

and the new Graphics card has these connectors

The GPU has the following warning:

So I think I need a new PSU

Maybe this one would work?

https://www.caseking.de/en/corsair-rmx-series-rm1000x-power-supply-80-plus-gold-atx-3.1-pcie-5.1-1000-watt/NECS-178.html

This PSU says it has:

Connections: 1x ATX 24-pin 2x EPS/ATX 12V (4+4-pin) 1x PCIe 12VHPWR (12+4-pin) 4x PCIe (6+2-pin) 3x SATA (4 connections) 2x PATA (3 connections)

Cables: 1x ATX 24-pin (610mm ±10mm) 2x EPS/ATX 12V 8-pin (750mm ±10mm) 1x PCIe 12V 2x6-pin (650mm ±10mm) 4x PCIe 8-pin (6+2) (650mm ±10mm) 3x SATA (4 connections, 850mm ±10mm) 2x PATA (3 connections, 750mm ±25mm)

But I have read that the Dell motherboard uses non-standard PSU connectors. So do I need an additional converter?