How much dry food should i give my 3 month old springer spaniel?

Our puppy is 3 months old and he weights 6.7 kgs our vet has told us he is a good weight. At the moment we are feeding him wet food and dry food however we are looking put him on complete dry food over the next few weeks. we have read the packet but it doesn't give a clear explanation of how much dry food over 3 meals should we be giving him please help