Precision 5820, how the DATA travels from the M.2 flex bay disks to the motherboard?

Hi, Trying to understand how the DATA travels from the M.2 flex bay disks to the motherboard. When I look into the M.2 flex bay I only see the power cable and temperature sensor cable, but I don't see where is the data cable, what I supose is that the data travels through the power cable, but asking to Chatgpt says that the power cable is not designed for transfer data. May can you explain what is the flow to send the data to the motheboard? 

My theory is that the power cable transfers the data to the backplane that is near to the psu, and from there there is two pcie cable that is connected to the motherboard where the data is traveling.

Thanks,

Cris