The cable of the Powerswitch in the case needs 2 Pins, but there are 20 Pins at the front panel connector of the Mainbaord. Where I have to plug in this Cable?
Are you sure you have the correct spare part,
519739-001 Power Button/LED Assembly?
It should have only one connector, referred in the manual like this:
- Connect the power button/LED assembly cable to the system board.
On the HPE ProLiant ML330 G6 Server - Remove/Replace Videos you can see this cable on the video Power button/led assembly (0:21-), and it is a single 20-pin cable for the whole connector:
Therefore, the HP ProLiant ML330 G6 Server Maintenance and Service Guide doesn't even have any guidance for the connector pinout, as it doesn't assume you would be connecting individual 2-pin cables.
The only 2-pin (red/black) cable involved should be the temperature sensor. If it's not connected for some reason, there's also a video for that on the same media library page. It seems to belong to the lowest 2 pins on the "reserved" (27) connector right above the fan 3 connector (26).