
At 9 weeks I'd pretty much go on appetite, so put a small handful in his bowl at each of four meals, fi it al goes in a couple of minutes, then maybe give a little more next meal until you work out what eh needs.
If he's really greedy and becomes loose cut him back a little.
The breeder can tell you how much they were giving them, expect pup to maybe eat a little less with no littermates to burn off more, so give them a ring.
Go by how he looks and feels as the amount he needs will alter.