You can run High Sierra without converting a drive to apfs, Apple’s latest File System. However, you might encounter some odd behaviors, or want to take use of the enhancements in apfs. If you did a command line installation to skip the apfs conversion or are just trying to upgrade a volume that wasn’t converted during the upgrade process,  Boot the Mac into Recovery Mode by holding down the Command and R keys until you see the macOS Utilities screen. Open Disk utility. Choose your boot volume. Click on the Edit menu Click on Convert to APFS When prompted with “Would you like to convert <thenameofyourdrive> to APFS?” click on…