Outdoor storage of more than one (1) motor vehicle with a storage license or not currently licensed is prohibited in any residential, commercial, or industrial zoning district; or of more than three (3) motor vehicles with storage licenses or not currently licensed is prohibited on parcels under ten acres in size in any agricultural zoning district; or of more than nine (9) motor vehicles with storage licenses or not currently licensed is prohibited on parcels ten acres or larger in size in any agricultural zoning district. Motor vehicles held for sale by a licensed motor vehicle dealer at said dealer's place of business in a zoning district where motor vehicle sales are permitted shall be exempt from the requirements of this section. With approved screening, the Board of Adjustment may determine the number of motor vehicles that can be stored outdoors provided the property owner has obtained all necessary licenses from the State or Iowa for vehicle recycling, salvaging, or similar license.