At the delivery month in September, the price is 3,500 yuan, and you are profitable. The price difference in 500 yuan comes from your risk income, because the price in the delivery month may be less than 3,000 yuan.
Futures is a zero-sum market. Only when you buy and sell can you make a deal.
Go directly to the exchange to get the goods on the delivery day (of course, you must first be an enterprise user who can issue VAT invoices). Don't worry about the stock exchange being out of stock.