Hi,
I tried the method you shown below but the unlock button did not appear when I entered my private key. Do you what I did wrongly here?
Thanks.
Open the MEW extension and click "Add Wallet"
https://i.imgur.com/m9hcjCP.jpg
You'll be redirected to the MyEtherWallet-Website.
Select the "Private Key"-Checkbox, then enter your private-key and click "Unlock".
https://i.imgur.com/8nYhy5O.jpg
Next assign a "name" and a password (the password will be the password for your keystore-file) and add the wallet.
https://i.imgur.com/yio1A27.jpg
Now open the extension and click "My Wallets".
https://i.imgur.com/WUGz72S.jpg
You'll be redirected to the MyEtherWallet-Website - click on the "View"-icon for your wallet
https://i.imgur.com/NI4fDpD.jpg
Enter your password and click "View Wallet Info".
https://i.imgur.com/Tk10N5A.jpg
Now just download your keystore-file
https://i.imgur.com/eICwtLH.jpg
Let me know if there are any problems