12 Months Interest Free Credit Cards Purchases

What is the best way to handle this big purchase?
Say I have $ 3500 cash in my account. I also owe a debt of $ 3.500 a Credit card with a 10% interest rates. I have to spend $ 3500 on home soil. My options are to spend the cash on the floor, or open an account 12 months interest free with the retailer, and spend that $ 3500 on my credit card to pay it off. Assuming that I can pay $ 3,500 within the window of 12 months What should I do?
If you can afford to pay the credit card immediately, I would do that … would be like winning a 10% the same, which is much more than they earn, leaving it in a bank account.