From Manual:
ONBOARD ROM BACKUP & RESTORE
The Axe-Fx II contains an internal FLASH ROM where PRESET BANKS and SYSTEM SETTINGS may be stored for speedy recovery without a computer. The contents of the FLASH ROM are not overwritten or modified during firmware updates or when you restore presets, banks, or the system from SysEx backup files.
Select the appropriate entry on the UTILITY: PRESET page and press ENTER to begin the backup or restore.
BACKUP BANK A, B or C copies a group of 128 presets to the onboard backup ROM. Bank A contains presets 0-127, B contains 128-255, and C contains 256-383 (or 1-128, 129-256, and 257-384 when DISPLAY OFFSET is turned ON). A meter indicates progress. It takes less than 10 seconds for a backup to complete.
RESTORE BANK A, B, or C reads a group of 128 presets from the onboard backup ROM and writes these into the onboard preset memories of the Axe-Fx II when you press ENTER to execute the selected function.