The transmission drain plug location on a 2005 PT Cruiser depends on whether it has an automatic or manual transmission. There's no single answer. You'll need to consult your owner's manual or a repair manual specific to your PT Cruiser's transmission type (automatic or manual).
Crucially: Incorrectly identifying the drain plug can cause significant damage. If you're not comfortable working on your car, it is strongly recommended you take it to a qualified mechanic for a transmission fluid change.