Since this is for meal prep, the most practical solution is to increase the volume of the batch without just making it watery. I would suggest dividing the soup into two or three separate pots. To each pot, add more of the main ingredients like unsalted broth, vegetables, and any protein you used. This way, you are creating a new, larger batch from the salty base. It's an effective method that saves the food and you end up with even more soup for your meal prep.