Even though iFixit doesn't have a Guide for this, we still have some resources to point you in the right direction. The connector the the power button is this one at the end of the top arm of the board.
[image|3274428]
You might also be able to use this YouTube teardown to get a better idea of were it goes. This is timestamped to see where the cable is located, but the whole video can be used for an idea of layout.
[video|https://youtu.be/QlkC6_AiinU?si=trYsdp0UCQ3YhlNA&t=344]