If your BTC was on Bitcoin Core, you won't have any "seeds"... you'll have private keys in WIF format. As you already have your private keys "exported", my personal suggestion for how to tidy all this up is:

1. Create a new BTC wallet in Electrum (https://electrum.org/#download) using the "Standard wallet -> Create a new seed" option - Write down your Seed Mnemonic and keep it safe!!
2. Send ALL your BTC from Bitcoin Core to address in new Electrum wallet (or use "Wallet -> Private Keys -> Sweep" function in Electrum)
3. Create a new BCH wallet (use "Standard wallet -> Create a new seed" option) in ElectronCash (https://electroncash.org/#download) - Write down this Seed Mnemonic as well and keep it safe!!
4. Use "Wallet -> Private Keys -> Sweep" function in your new ElectronCash wallet to move all the BCH from your Bitcoin Core private keys into your new BCH wallet.

The end result of this will be that all your BTC will be in a new Electrum wallet, backed up by the Seed Mnemonic (aka "12 words")... and you'll have access to the BCH via ElectronCash (again, backed up with different "12 words") and you can do whatever you like with it (HODL, send to exchange, trade with people etc).

Also, now is a VERY good time to move your BTC, as fees are super low... I've had "next block" confirmations with fees as low as 1 sat/byte recently