You can do this via declarative tool, for example: process builder.
If you want to automatically create a Car record whenever an Order record is generated, that means your process builder must be based on Order object, then you can either choose only to run it when record creation only OR also when edited. Normally I would choose on both record creation and edit, because most likely there should be more actions to add on when record is modified.
In the Decision Node, use
ISNEW() formula to indicate that your process builder only run on record creation event only.
In the Action Node, you can either use actions "Create a Record" or "Quick Actions" (Lightning only).
I assume your Order would have the lookup field to Opportunity and other object as well.
If you choose "Create a Record", you can assign the lookup field referenced from the Order.
I would choose Quick Action because it is more flexible: supports predefined field values, can be used as button, or called via apex class.