How much to feed my corn snake

[BirdBones]

Hi everyone! New user here, first time posting.
I was recently given a corn snake. They told me he'll be 10 years old this May, but he seems a little small to me - he's about 3.5 inches around, and about 38 inches long.
The people I got him from said they were feeding him 4 fuzzies a week, but last feeding I gave him two large hoppers instead and he took them down just fine. I'm wondering, is he small for his age, and if so is it because of what he's been eating? Should I increase the size/quantity of food? This is my first snake, and I want to make sure he's happy as can be.
Thanks, everyone!