It is a simple USB type C to Displayport adapter. You can easily find it at amazon.com. And then I just used a simple Displayport to Displayport cable to conect to the adapter.
Since the lenovo 910 is 4k, to get the resolution up to 4K UHD at 60Hz for a clear, sharp picture, you specifically need to use the displayport on your Monitor. If you use the HDMI port on your monitor, it won't matter if you're using the USB-C or a normal USB port on your computer. The resolution won't reach 4k @ 60hz. It'll be 4k @ 30hz, at the best scenario.