Switching car seats

Al

When did/is everyone making the switch from your infant carrier to your grow w/ me car seats, my babe is inching is way to 30lbs and is at about 29inch (car seat says 30lbs or 31inchs) but he still can’t completely sit up right I’m concerned with this because if we go to the store and I don’t have his carrier he’ll teeter over in the shopping cart. I’m obviously a first time mom 😂