Yes, if all of the cars are on the same policy then even though there are multiple cars there will be only one policy number. You will normally be issued an insurance card for each vehicle to carry with you and show to law enforcement if requested to do so.
Each card will typically have the policy number, policy holder(s) name, description of the car and its vehicle identification number (VIN) on it. So while all of your cars are under the same policy number the insurance cards will differentiate between them all and list the car that the card is for on it.
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