It should tell you on the can... different brands contain varying amounts of specific nutrients and each has their own reccommended amounts to feed (as a starting point) by weight of the puppy, same with kibbles.
Note if the food is 'Puppy' food or 'For all life-stages'. Puppy food is higher in protein and other nutrients. 'All life stages food' compensates by increasing the amount/times fed to the puppy to meet his/her nutritional needs. Also include any treats fed throughout the day. If too many treats are given, the pup/dog may not eat the Daily Reccommended Amount of his/her dog food.
To feed canned and kibble mixed for each feeding, take the daily reccommended amount for each and divide by 2. Then combine those results, divide by the number of feedings per day.
To feed canned as the main meal, and freefeed kibble on the side, feed the reccommended amount of canned at each feeding. Measure the amount of kibble you are going to leave out. I would not put out more than 1/2 of the daily reccommended amount, to prevent overeating. When freefeeding, it is important to measure the amount set out daily for the dog/pup as it is very important to know exactly how much they are consuming per day.
These are basic guidelines, you may need to make adjustments depending on your puppy's/dog's activity levels and weight. Check your dog often, a few times a week, by feeling the rib cage. You should be able to feel the ribs, and a layer of fat between them and the skin. You should not be able to see the ribs.
Puppies go through growth spurts, as they grow their food amount will need to be increased. Check weights regularly. This is also important to do for the adult dog and the senior dog, as weight changes can be one of the first signs of a medical issue.
Here's a link for determining a dog's Body Condition:
How to Evaluate Your Dog's Weight - For Dummies