There is no real reason to use the Kindle Personal Documents service unless you need to sync between multiple Kindle devices/apps.
However, if you do want to, for whatever reason, it has been reported that Amazon will accept dual-formatted MOBI. Under Preferences ==> Output Options ==> MOBI tab, change File Type to "Both".
Then, when converting to .mobi it will include KF8 and the KF8 section will be sent via the Cloud to your Kindle if the device supports KF8 -- which yours does.
See here:
https://www.mobileread.com/forums/sho...d.php?t=215440