Once you have exported your private keys using BIP39 tool you should get a list of addresses and keys. Please copy the Private key from the box where you can find your Ethereum/Erc20 address with your holdings.
Now go to MyEtherWallet and click on ''Send Ether & Tokens" so that you will get the options on how to access your wallet. Choose here the option to access your wallet with a Private Key.
After pasting your Private Key you can click on "Unlock" and you will then have access to your Ethereum/Erc20 tokens.