If you want to trade USDCUSDT contract (which is future trading pair), you are not converting USDC to USDT but you want to make money from trading the pair. Some exchanges like Bybit have such pairs but I do not trade stable coins and stable coins pair on derivative exchanges.

Go to spot and search for USDC, you will see USDC/USDT pair on BingX which is what you are looking for as you want to convert USD to USDT.