1 for Gohan, 1 for Vegeta, 1 for Krillin. So I guess 3? Unless they show that he lost the others?
I suppose he could have more in the Capsule Corp spaceship (made by useful Bulma's father). If so, he ended up far from the ship and severely injured, so couldn't go to get them. But in that case he would have told Gohan to give Piccolo a senzu bean from the ship, rather than just saying to find Bulma and leave Namek (which would be in Nameless Namek's ship, so not in Goku's ship where they could perhaps easily happen across the senzu).