Where is the trans dip in a 2004 Cavalier?

If it is an automatic, there isn't one. As stupid as it seems, the oil level is checked with a level plug located in the side of the transaxle that is only accessible when the car is on a hoist. The car must be level, transmission warm and on a level surface (hoist) when removing the plug to check. The transmission is filled by removing the vent located on the top of the transmission.