Can't convert internal SSD to APFS
In my MacBook Pro mid-2010 running High Sierra 10.13.6, I'm upgrading the drive to a 1 GB SSD (SanDisk 3D SSD). I replaced the drive, booted with another external backup drive, formatted the new internal SSD to APFS, and then used Disk Utility to restore the old drive to the new.
This process converted the SSD to regular Mac OS Extended (Journaled) formatting. When I select either the drive or the volume and go to Edit > Convert to APFS, it is greyed out. This happens whether I boot from the internal SSD or the old drive externally (both High Sierra).
How can I convert the SSD to APFS?
MacBook Pro (15-inch Mid 2010), OS X Mavericks (10.9)