Only marketplace which has all the coins you are interested in (BCH, TRX, DENT and SC) is HitBTC (
https://hitbtc.com/). This is one of the popular exchanges, so just open the account here, transfer the BCH to the wallet on their site and than change BCH to BTC and ETH. You have to use both values, because on HitBTC you can buy DENT only with ETH, and SC only with BTC (for TRX you can use both).