* On a sticker inside the driver's side doorjamb. This sticker often lists the vehicle's specifications, including the transmission type.
* In your owner's manual. This is the most reliable source.
* By checking the transmission itself. The transmission case may have a casting number which can be used to identify the transmission type.
Once you know the transmission type (e.g., 4L60E, 4L80E), you can then search online (e.g., using Google or a parts website) for the correct fluid capacity for a *fill* and a *total* capacity. The fill capacity is how much fluid you add during a fill, while total capacity is the total amount the transmission holds. These are different numbers.