Yes, you can use the DJI Mini 3 Series Intelligent Flight Battery with the DJI Mini 4 Pro drone. However, when using the DJI Mini 3 Series Intelligent Flight Battery, DJI Mini 4 Pro’s propulsion performance and flight time will be reduced. The total weight of the drone will also exceed 250g, meaning that you cannot fly in the A1 subcategory without having an A2 CofC. If the weight does exceed 250g, and you do not have an A2 CofC, you will need to fly in the A3 subcategory, ie flights far from people.