First of all this is not the right section to ask for help, try to move this thread in to beginner section . Secondly you can not just convert this to BTC, what you need to do is :
1- Transfer this Ncash to an exchange, you can pick the exchange you like from coinmarketcap.com search for Ncash then press the markets TAB and a list of active market will appear do some research and pick what you like, I would recommend Binance .
2- After your Tokens transferred safely to the exchange you picked, you need to sell them for BTC .
3- After you sell the tokens, now you have BTC in your exchange, you are free to transfer this BTC to your blockchain wallet.
-For a detailed step by step on how to use Myetherwallet you can use search function here or at google and always make sure you are connected to the real Myetherwallet and make sure it is secured .
-make search on how to make exchange account and how to make sell and buy orders, it is pretty simple and easy .
That friend of yours should have touch you this, jumping in crypto without even knowing how to transfer tokens and how to sell for BTC is really not good and you will probably end up getting scammed .
