its best if you can breastfed exclusively. to increase milk supply you can drink more fluid and soup. You can make green papaya soup with pork ribs and red date with dried longan.
About suckling, normally the nurse will teach you to nurse 15 min on each breast, then when the baby still want milk, you will have to add formula or give the milk that you have expressed earlier.
From my own experience if they are suckling and you hear the swallowing sounds means they are drinking.
Congrats on your baby. Is it boy or girl.
All the best!