If you don’t see “This PC”, look for the name of your computer. It’s next to an icon that resembles a computer monitor.

The amount of space each hard drive has is listed below the drive name in File Explorer. Right-click the hard drive with the amount of space that matches your external hard drive.

NTFS: This file system works well with Windows, but may not be writeable on Mac or other systems. Select this option if you only plan on using your external drive on Windows computers. exFAT: This is usually the default file system. It works well with all versions of Windows and recent versions of macOS. It may require additional software on Linux, but is still supported by more devices than NTFS. Select this option if you plan on storing large file sizes and plan on accessing your external drive on other devices, such as macOS. FAT32: This is an older file system that can only store files that are less than 4 GB. It is, however, compatible with more devices. Select this option if you don’t have any large files and need the largest compatibility across multiple devices.

Alternatively, you can find the Disk Utility app in the Utilities folder, which is inside the Applications folder in Finder.

APFS:. This is the newest Apple file system optimized for Solid State Drives (SSDs) and Flash Drives. Select this option only if you have an SSD or flash drive and plan to only use the drive on Mac OS High Sierra or newer. Mac OS Extended: This has been the standard Apple file system since 1998. Select this option if you have a mechanical or hybrid hard drive, if you are using an older version of Mac OS, and only plan on using your external hard drive on Mac computers. exFAT: Select this option if you need your hard drive to be compatible with multiple devices, including Windows computers.

Some other popular data-cleaning tools are DBAN Drive Cleanser by Acronis, and CBL Data Shredder. [3] X Research source

Be careful not to select a disk drive you need, such as your Windows installation drive.

If you have the registered version of KillDisk, you can select more accurate erasure methods using the drop-down menu next to “Erase Method”. You can also check “Verify erasure of [disk percentage] of each disk. "