Difference Between Employer ID Number and State Tax ID Number

Is there a site or information out there that is available to see samples of each state's sale tax number. We host a private trade show and want to make sure the general public is not admitted and we require them to bring along the state sales tax number. However, because each states differs we are unable to really verfiy whether that number is correct or they are just creating a number. If we even would know the format for each state would be very helpful. Can you help?