To find out for certain:
1. Check your owner's manual: This is the best source of information. It will specify the correct fluid type for your vehicle.
2. Look on the transmission dipstick: Sometimes the recommended fluid type is printed on the dipstick itself.
3. Check the transmission identification tag: This tag is usually located on the side of the transmission. It will have a code that you can use to look up the specifications online. You'll likely need to look up this code in a repair manual or online database.
Important Note: While Dexron VI is generally backward compatible with Dexron III, using the wrong fluid can damage your transmission. Always use the fluid specifically recommended by your vehicle's manufacturer. Don't rely on generic advice – checking the sources listed above is crucial.