One of the 35 supermarkets refers to the supermarkets in Sam. Because we can't find Sanwu Supermarket, the member store in Sam must be a member to purchase goods. Anyone who holds a valid ID card or other valid documents can apply for a membership card. The annual fee of the main card is 260 yuan/year. If you don't want to buy a card, you can only find someone with a membership card.
Sam Supermarket generally refers to Sam member stores, which is a high-end member store owned by Wal-Mart, a fortune 500 company.