If you have to change your plaques d'immatriculations because you've bought a new car or changed departement just go to a garage. Bring your carte grise, you won't have new plaques d'immatriculation unless you can show your carte grise.
"Bonjour, je voudrais faire changer les plaques d'immatriculation de ma voiture"
It will take only a few hours and cost around 50 euros (it depends, prices are free so maybe it's worth checking different garages before you choose one).
Back to the "carte grise" article