Hello yhzs8,   I have one image available I'm attaching to this post #DPHJ8 - ASSY,CBL,PCIE,GPU,15G,2U ASSY Cable PCIe GPU 2U I hope this helps.  
According to this page [URL] the R750 has only 12 pin connectors for GPU power, the previous R740 has 8 pin GPU power connectors for each riser. How can we connect our FPGA card (using 6/8 pin GPU power cable from R740) in R750?
R750 GPU power connector