Car seat

Has anyone bought a convertible car seat that has a removable base?? I really want a car seat that is going to last more than just the infant stage but I’m having a hard time finding one that has bases that it can click into. It seems like almost all of the infant car seats have bases but the convertible ones don’t?? What am I missing??

My husband and I both want to have a base in our cars and then we’ll need a 3rd one for my moms car since she’s going to be our primary childcare.

Thanks so much! Also if anyone has any other ideas about how they handle the car seat situation please me me know :)