Disk Utility - Find External Hard Drive Format
The following instructions explain how to use Disk Utility in order to determine the format of an external hard drive.
1. Ensure that the external hard drive is connected to the Mac and is mounted.
2. Single click anywhere on the Desktop and press SHIFT+COMMAND+u on the keyboard. This will open the Utilities folder in a Finder Window.
3. Double click on the Disk Utility icon to launch Disk Utility.
4. In the left sidebar, single click on the icon that represents the desired external hard drive, or specific volume (volumes are indented). In the picture below, the selected volume is named "500GB Time Machine".
5. Single click on the Erase button at the top of the window. (Don't worry, the volume will not be erased)
6. The format of the external hard drive volume is displayed on the Format menu. Do NOT change this menu or click Erase (just below). If the volume needs to be reformatted, please back it up prior to reformatting.
7. Click Cancel to ensure that you don't accidentally Erase or reformat the volume.
External Storage Device Recommendations