I don't know how what is purpose of this post. An old of forum asking the way how to buy Usdt.
Well if you want to buy through credit card then Coinbase pro is best if it's available in your country. You can also try Binance and buy through P2P service if you don't want to use credit card. Kucoin is also best option. When you buy stable coin then you can trade Bitcoin or any other altcoin.