In a large bowl, add the rhubarb and sugar; stir to coat evenly.
Cover the bowl, and place it in the refrigerator overnight.
The next morning, place the rhubarb mixture and the strawberries, in a large kettle.
Bring the mixture to a boil over medium heat, then lower the heat just a bit, and gently boil for 15 minutes (stirring constantly).
Add the crushed pineapple, and cook for an additional 5 minutes.
Turn off the stove, add the boxes of dry gelatin powder, and mix well.
Transfer the jam to the sterilized glass jars, and cover the jars with the lids.
Cool the jam to room temperature, before storing the jam in the refrigerator or freezer.
Yields: 7-1/2 cups of preserves.
Note: If using store bought frozen sweetened strawberries, you may want to decrease the amount of sugar to 3-1/2 cups. I however, used strawberries which I prepared myself and had froze them. They're not as sweet as the store bought, so the 4 cups of sugar I added, was the right amount to add to this recipe.