Yep, so one end to the GPU (you may have a spare 6 or 8 pin cable, this is fine it doesn’t get plugged into anything) and then the other end to the Riser

But make sure this isn’t just a GPU cable you have lying around, if it is make sure the pinout is correct or you will blow your riser card

Nah, that connects to your GPU you want to you, not the motherboard

You can make a power cable, the pinout is non-standard, but people have made them and posted schematics online. They do sell them on ebay but it’s a gamble if you get a good or bad one.

Does your XD have the risers with power taps on them? Riser 1 and 2 (or 2 and 3) should have 8 pin power taps that will supply power to your 3060.

Make sure you have dual 1100w power supplies, and the server in a room you don’t use, as the fans are likely to ramp up since the card is likely not a blower style card and the servers fans will work harder to keep it cool.

I’m sure someone else will come along that has more experience than me, and give you some more advice

Don’t buy Flashforge unless you want to hate your life. They were the first printer I ever bought and unless things have changed they use a proprietary slicer that’s years behind anything else, and they will claim it works with other slicers…until you discover you need to figure out all the settings yourself, including start and end codes