Which drive letter should I choose in Step - 1 of CardRecovery

When you connect your camera to your computer, if a new drive letter appears in "My Computer", that drive letter should be the needed one.
If your camera does not appear as a drive letter in "My Computer", an external USB card reader may be necessary for almost all data recovery software programs. You may find such card reader in local computer shop, or Amazon.com. They're convenient and very inexpensive.