What is the cheapest & safest way to cashout altcoin ??
Please name the best exchange from where we can trade in usd and cashout.
Since you mentioned USD and not USDT, then I think you need to exchange them to bitcoin or ethereum first, and only after that you can exchange them to USD. As for what exchange to use in order to convert BTC to USD, I would recommend Bitstamp, Gdax, Gemini, and Kraken. I don't use them all, I'm just mentioning the biggest exchanges with USD, so you should make some research about them.