He is here

[John1982]

so, the smallest f/t pinkies I see online are listed as extra small, 1.5 - 1.9 grams each. He can eat these? And how many do you think he will consume before needing to move up to a larger mouse? Feed how often?

Corny is a looker, congrats. Yes, he can take a mouse pinky - no problem. Most frozen rodent suppliers sell pinky mice in bags of 50 or 100 so you shouldn't need more than 1 bag if he's the only snake you're feeding. Depending on the size of prey/snake, once a week is a fine feeding schedule for most growing colubrids. Near the end, as you finish whittling down that bag, you simply offer more per feeding to make up for his growth. When the bag is nearly depleted, reassess his size and order something more appropriate.