Power Supply for DELL Precision Tower 5810

Hello, I would like to ask about a compatible power supply for the DELL Precision Tower 5810. I currently have a 685W one, but I would like to upgrade from a GTX 1080 TI to an RTX 3090 or 3090 TI. But I read somewhere that Different power supplies, for example 1300W, have different connectors, so I want to ask which one I should use or what I should do so I don't ruin my DELL because I wouldn't want that. Thank you in advance and have a nice rest of the day.