Almoast every exchange have option to trade with USDT or TUSD. They are both tokens that imitates American Dolar (every USDT/TUSD was print when company recive USD to their bank account from users. Thats why they are stable. you can also convert it back to USD). USDT is more popular. TUSD i newer, less popular but it is subject of regular audits. Which gives investors feeling that it is safer (there was lots of rumors that Tether (UDST) is printing more than it should - more than it gets $$ and if anyone decide to reconvert their USDT to USD there will be not enought USD - but that's only rumors).

You can check on coinmarketcam if specyfic exchange has trading pairs with TUSD or USDT. I highly suggest you binance. Thats my favourite one. It has USDT pair with NEO ADA XRP BCC BNB LTC ETH and is close to aslo supprot TUSD.

And there are others less popular like TryNinja said: