Expect a drain and fill to require approximately 3-4 quarts. This only replaces a portion of the fluid.
A complete flush and fill (which is more thorough) will require significantly more, potentially up to 10-12 quarts. However, even with a flush, not all fluid is removed in a single pass. Multiple flushes may be needed. It's best to consult your owner's manual or a repair manual specific to your year and model (including the exact transmission type) for the most accurate information. These manuals often give the fill capacity rather than the total system capacity.
In short: You should plan for at least 4 quarts for a drain and fill, and consider much more if you are doing a complete flush. It is crucial to check your owner's manual or a reputable repair manual for the precise specifications. Using too much fluid can be just as damaging as using too little.