Transmission dipstick in a Hummer H3 2006?

The transmission dip stick and fill tube is near the firewall on the passenger's side it should have a yellow or red handle.

This guide shows the job being done on a similar model but the procedure is the same. (scroll down)

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

AUTOMATIC TRANSMISSION CAPACITY
Pan Removal .................... 5.7 Liters (6.0 Quarts)
Overhaul .................... 10.6 Liters (11.0 Quarts)

NOTE: ALL capacity specifications are approximate. When replacing or adding fluids, fill to the recommended level and recheck fluid level.

Transmission Fluid Checking Procedure
1. Start the engine and operate the vehicle for 15 minutes or until the transmission fluid reaches an operating temperature of 82 - 93°C (180 - 200°F).
2. Park the vehicle on a level surface.
3. With your foot on the brake, move the shift lever through each gear range. Pause for about 3 seconds in each range, ending in PARK.
4. Apply the parking brake and let the engine idle for 3 minutes.
5. Remove the transmission fluid level indicator. Wipe the indicator clean. Insert the indicator. Give the indicator a full twist in order to close.
6. Wait 3 seconds and remove the indicator.
7. Read both sides of the indicator. The fluid must be within the hot cross-hatched area using the lowest level reading.

CAUTION: The engine must be running when the transmission fluid fill plug is removed, or excessive fluid loss will occur. Transmission fluid may be hot. Since the actual fluid level is unknown, stand clear when removing the fill plug. Have a container ready to capture any lost fluid. Do not turn the engine off with the fill plug removed, as you can be injured by hot transmission fluid being expelled out of the oil fill opening.

Check out the images (Below). Please let us know if you need anything else to get the problem fixe