Car seat help

Bethany
Ok everyone I'm located in U.S. For anyone who will ask
My daughter is almost 3. I still have her rear facing she has 12 more pounds or 5 more inches.... Trying to figure out what's next car seat wise?
Should I go with a like a back booster or go with one that you can still use harness on.... Car seat weight transition in 40 pounds and both seats are weighted for that?
I'm assuming she will be 3 1/2 or 4 before she out grows