Are you going to redeem the BTC from your casacius coin?
Are you sure it's a minikey or a private key?
You need to type them one by one when importing there are many wallets that you can use I suggest you import it in a secured PC with Electrum.
Watch this video how to redeem Casascius coin from here
https://www.youtube.com/watch?v=y1yydfYJFwA