I suggest you create an array of the type of your “car bp” somewhere easily accessible, your gamemode for example.
Inside your car bp, add an Arrow component where you want your character to spawn.
Every time a car spawns, add it to the array you’ve created earlier, then create a function like this one:
When all your cars are spawned and reach their final location, simply loop through your car array and execute the function above for every item within it.