Your business may require a vendor license to make sales in the state of South Carolina. Visit The Department of Revenue to register your business as a temporary vendor.
Department of Revenue site for SC: https://dor.sc.gov/tax/registration/faq.
If your business does require that you obtain a temporary vendor license for the state in which you are exhibiting, you also need to submit payment of sales tax after the conventions. Sales and use tax forms can be found at the website mentioned above.
Questions about taxes or licenses should be directed to the professionals at each state department.
South Carolina Department of Revenue
Columbia, SC 29214-0140
Summary: Every person who engages in business in this state as a retailer must obtain a retail license before making any sales. This includes sales made online and persons who make infrequent sales in this state. If you have more than one business outlet, you must have a separate retail license for each location.