Emachine t2885 power button don't come on because the power cords came out from the mother board and I don't know where they go pw. sw. hdd

The motherboard in the machine should have some identifying labeling on it. Determine who made the motherboard and then visit the vendor's website to obtain a manual for the board. The manual usually will have pinout diagrams for all the board's connectors and headers. Alternatively, the front panel header (two rows of pins) along the front or bottom (left) edge of the board may be labeled on the board itself.

Also, if the front panel came off with enough force (abuse) to disconnect all the front panel wiring, the front panel header pins may be bent and need straightening first.