In that case, TrustDice doesn't have it anymore.
I am not sure that it's gone. According to one of their support articles, it depends on the player's location. They even suggest using a VPN if the feature isn't offered to you in your account. The information they offer is a bit contradictory though.
Here, take a look:
Unfortunately, we do not offer an exchange service on our platform.
Thus, if you wish to exchange your currency, you must first withdraw your currency to your personal wallet and exchange your currency through your personal wallet or through an exchange site.
Then there is this:
Alternatively, you can always choose the option “Deposit with Altcoin” where you can exchange any crypto you have to BTC, ETH or EOS. If this option is not available in your region, you can use a VPN to change your location.
I can't share a source to this info because it's information available through their live chat.
This makes it sound like the exchange only works when the coins are being deposited to the platform. I checked with their support and they confirmed that to be true. When you are on the deposit tab, you can click on the "More" option in the list of coins, and that allows you to select which crypto you are depositing and which one you want to receive. The receiving one can only be BTC, ETH, or EOS.