We would like to mention that this forum is supported in english so we would appreciate if you could post any additional comments in this language.
As we understand, you are installing an Intel® SSD 750 Series 2.5in to your Asus Z170 ROG MAXIMUS VIII EXTREME, and you would like to know how you need to connect the 3 connectors in the U.2 cable.
The 3 connectors are required for the SSD to work. In one end there is a MINI SAS HD that connects to your motherboard, on the other end of cable, you will find the SFF-8639 connector that goes to the SSD, and also a SATA power connector that must be plugged to a SATA power cable coming from the Power Supply.
Here is an external video that clearly illustrates this. The motherboard in the video uses a M.2 to U.2 adapter, however, your motherboard has built-in U.2 connector:
*NOTE: This link is being offered for your convenience and should not be viewed as an endorsement by Intel of the content, products, or services offered there.
https://www.youtube.com/watch?v=2BWXmfCbBSg MSI® HOW-TO Install NVMe U.2 SSD with MSI Turbo U.2 Host Card - YouTube