So I’m not quite sure where to put this but...

We have the Keyfit 30 for an infant seat and I have no idea how to figure out when my baby is too big for it and what kind of carseat comes next because the convertible seem too big for him? He’s currently close (I’m guessing) to 20ish lbs and 27ish inches. I also may have lost the manual while moving...oops! Anyways I’m trying to figure out when we switch him over and what type of carseat we switch him over to. I also have no idea if I take the inserts it came with out to accommodate his growth or if they are necessary? Any pictures of what we move to next and input of around when to know when to make that switch would help! Thanks in advance, y’all!