I'm so happy to hear that he is settling in.
BIG problem. Yes, 10cc is the same as 10 ml but you can't use that. They deliver WAY too fast. The risk of aspiration pneumonia is HUGE with a 10cc syringe. You should use either a 1cc or 3cc syringe. You can probably get away with a 3cc syringe at this point. No matter how big they are I never use a 10cc syringe.
I'm confused by the amount. You said 3. Are you saying 3cc (ml) or 3 of the 10cc syringes full. That would be 30cc (ml).
You need to get a scale. The amount of formula is based on the weight.