Am I wrong or is my husband?

First time mom here but I need advice and I am pretty sure I am right andmy husband is wrong but I can’t get thru to him.My daughter is currently still in an infant carseat. I am wanting to get her a convertiblecarseat before she maxs out on the infant one. My husband says I can easily take the convertible one out like we do the infant. I told him no it doesn’t work like that. He takes her to the babysitter sometimes in his work car so he needs something he can take out when he drops her off. I am at such a loss at what to do?