You can use Windows BitLocker using AES 256 bit encryption.
The default will always be AES 128 bit when using BitLocker but you can change this if you'd like that extra bit of encryption strength.
If you bring up a the RUN command (Window+R) and type: gpedit.msc
You will then be presented with: Local Group Policy Editor
- Click on Administrative Templates -> Windows Components
- Double click on 'BitLocker Drive Encryption'
- Then to the left click on 'Choose drive encryption method and cipher strength
- Click enable
- Choose AES 256
- And apply
When you have finished the above instructions, insert the drive, password protect the drive and save the key for yourself somewhere secure.
Then next -> choose to encrypt the drive
If you don't want to do all this, you can stick with the default 128 bit encryption strength.