blockchain.info didn't introduce seed based accounts until early 2016 i think so it'll be an old school private key account.
you'll need to open the blockchain.info account, which must be a separate one, send it out and then retrieve the private key. use a qr code generator to turn the private key into a qr code and then sweep it into the coinomi wallet.
DON'T DO THIS! (In the way I understand it at leastL).
If you send bitcoin to another wallet, the bitcoincash does not go with it.
The bitcoin cash will remain in the first wallet.
And I'm not sure you can export private keys in the new interface using old wallets (people have complained in other forums that they can't sign transactions/access priv keys from their account which means they normally have to contact support for help).