Sort:  

I am certainly not an expert on ETH or MEW but do know that ATS tokens, which are probably ERC20 tokens in ETH, cannot 'just be converted' in MEW. MEW is just a wallet, not an exchange.

To convert ATS to ETH, you will need to transfer ATS tokens to an exchange and sell them there for ETH. First, ATS tokens would have to be listed on an exchange.

Like I said: first ATS needs to be listed an an exchange. Then, you need to have an account at that exchange, move the ATS tokens from MEW to that exchange and sell those ATS tokens. The proceeds can (if ETH) be moved back to MEW.

S that means there is no such provision for internal swapping in between ETH and ATS in MEW and second question is that will the ats token be listed in bittrex and if so in how many days after 14th.

Thank u..

I think there is no exchange yet that has ATS listing scheduled. But listing will not happen anyway before 14/9 because the ATS tokens have not been issued yet.

Just wait until the ATS tokens have been issued and listed on an exchange. As of then, you can pursue a sale of your tokens.