Cool Whip is a non-dairy whipped topping that is in plastic tubs and frozen. You generally thaw it out before using it. It's like whipped cream, but it doesn't have any real dairy in it. It's really just a mass of chemicals. You can whip cream until it's stiff, adding a tiny bit of sugar, but it will contain a lot more calories than Cool Whip since you are dealing with real cream.
Jello gelatin would be like your Jello jelly. Just check to see if the serving size is right. Most recipes that call for jello use the 4 serving size.
I moved you to the regular Foods forum because this is probably the best place to get food substitution advice