The update is being pushed over-the-air currently. The OTA is arriving with the software versions G532GDDU1AQE3 and C900FDDU1AQE6 for the Galaxy J2 Prime and C9 Pro respectively.
If you don’t receive the update just yet, fret not! It might take a while for the update to reach all the handsets. So, you will without any doubt receive the update sooner or later. If you can’t wait, however, you can check for it manually by heading to Settings > About Device > Software Updates.
As is the case with all the security patches, you can expect the update to bring fixes for several bugs alongside security and stability improvements to both the devices.
Make sure you backup your personal data before you hit the download button. A backup always comes in handy if things go south. Also, switch to a stable Wi-Fi network before downloading the update to avoid additional data charges.