Help with private key

I cannot seem to figure out how to view my private key. I tried using the .json file. I have tried the site where you type in your seed phrase, but PolkaDot isn’t listed as a coin that you can pick. I am trying to transfer Polkadot from trust wallet to Polkadot{.js}. When i enter the address to send from Trust, i get a message that says it’s not a valid Polkadot address.