Assuming you are using a standard 8-oz. cup and Folgers Classic Roast Ground Coffee, the ratio of coffee to water is 2 tablespoons (or 1/8th cup) per 6 fluid ounces. This means you would need 12 tablespoons, or 3/4ths of a cup, of Folgers for 6 cups of coffee.
If you're looking for a stronger cup of coffee, you may want to use more coffee grounds. For example, if you wanted to use a ratio of 1:16 (coffee to water), you would need 1 full cup of Folgers for 6 cups of coffee.