Here is a quick look at the Ultimate Kombat Kodes to unlock Ermac, Mileena & Classic Sub-Zero in UMK3.
note: codes are entered on stick/pad for player 1 AND player 2 aka YOU NEED A TOTAL OF 2 STICKS or PADS!
HOWEVER On PS3, you won't need 2 sticks/pads; enter the code for player 1, hold the PS button and reassign the stick/pad to #2 (the game will pause) and then enter the code for player 2. Much easier method and makes it possible if you only have 1 stick/pad.
The order you need to press the buttons is just like arcade which starts from the top left button (high punch) and goes down, to the right, then back up like a "W".