You only have one ADA deposit address & this is where you put it. Once the ADA shows up in your wallet you can trade any ADA/* pair that is supported by your exchange.
I think I am understanding your question , You can transfer your ada to your exchange , and then convert it to any fiat currency that you desire that is supported by your exchange a direct exchange means less transaction costs than having to go through a X pair , the price difference between the pairs is directly proportionate to the value of the fiat currency . i hope this clears it up
cheers Milan