LHR RTX 3070 16 pins, help!

I'm about to buy '' risers '' and unfortunately my 3070 has 16 pins to connect, I know that the '' risers '' need power from the same source, I don't know what to do.
I have 2 sources of 600 and I am going to connect a RX 470 and a RX 590

both use all the pins of one source, but the 3070 uses all the pins of the other source, the riser does or needs to have the same power supply, what can I do?