My 9 week old baby likes to suck on his hand to self soothe. He will only take paci if I'm holding him to sleep. What can I do to break the habit?

Ok. At 9 weeks it is a natural instinct to suck on thumb or hand. No need to discourage this.
Train him. You can train him to hold the pacifier but putting his hands to the pacifier. After 1-2 months, when his gross motor development milestone reaches there, he will hold it himself. Try it.