I assume you have a HoF or similar RTX 2080 Ti because otherwise I don't know of any card that needs 3x power connectors.

However, the power supply is SLI-capable, which means that you have 2x 2x8 pins on the separate SLI connectors, i.e. 2x 8 pins per connector on the power supply. Ergo in SLI 2 "normal" RTX 2080 Ti with 2x 8Pin each works wonderfully.
If you need 6 connectors because you want to use your monster card in SLI (4x 8 pin and 2x 6 pin) I recommend to use the SLI cables for the 8 pin (marked with VGA) and to use an additional 4-pin Molex connector for the respective 6 pin by means of an adapter. This way you have a clean distribution.

Hope the answer helps