Where is the trans dipstick?

There isn't one. There is a check plug underneath on the right side of the transaxle. The engine should be running, at operating temperature and the vehicle should be level when the level is checked. The fluid level should be even with the bottom of the opening when checking the fluid. You need to raise the vehicle on a hoist or drive it over a pit to accurately check the fluid. The check plug has an 11mm or 12mm head on the bolt.