The police are not required to show you the inventory before they take your car. However, they should provide you with a copy of the inventory as soon as possible. If you do not receive a copy of the inventory, you should ask for one.
The inventory is important because it can help to protect your rights. If the police find any contraband in your car, the inventory can help to prove that you did not know about it. The inventory can also help to prove that the police did not plant the contraband in your car.
If you are arrested by the police and they impound your car, it is important to remember that you have rights. You should ask for an inventory of your car and you should get a copy of the inventory as soon as possible.