The Electrum wallets will only sweep keys in WIF format (I think).

You can go to https://walletgenerator.net or liteaddress.org

once there skip through there generator and click on Wallet Details.

Paste you private key in there and it will return you the WIF format of your private key. It should start with a "6"

Then go into Electrum and sweep that.

If you don't trust the only services I think you can download their source and run them in an air gaped environment.