[Samsung Galaxy J3 (2016) Guides, News, & Discussio] GN9166:
The definite guide to rooting Samsung Galaxy J3(2016) SM-J320FN & FRP Locked Bootloop

As first I have to say, I had to create a thread in Q&A because of the low rank, but I am sure this can be moved to the J3 section as there are many questions on how to gain root access to this device. This guide can work on the SM-J320F model as well, but it hasn't been tested on other models, so don't try it !

Lets start :

Dont forget to Backup all your data before the process !!!

1. Tick USB Debugging and OEM Unlock in Developer Mode (OEM has to be ticked to unlock the bootloader)

2. Connect to PC with USB Cable and open Odin

3. Power off and reboot into Download Mode (VOL.DOWN+HOME+POWER)

4. Add twrp.zip to AP tab

5. Untick Auto-Reboot and Start

6. Wait to finish

7. When it's finished hold (VOL.DOWN+VOL.UP+HOME+POWER) to Power Off

8. Load into TWRP Mode (VOL.UP+HOME+POWER)

9. In TWRP first go to the Wipe Tab, check Cache and Data and click Wipe

10. Copy SuperSU into internal memory from your PC

11. Go back to TWRP and select Install, select the SuperSU from the internal memory and click install without ticking anything, then reboot

12. Wait for the phone to reboot, it may boot-loop a few times, and it boots slowly but dont interrupt the process !

13. From there on, check the root status by downloading Root Checker from PlayStore

KEEP OEM-UNLOCK ON ALL THE TIME, IF YOU DONT WANNA END UP WITH A BRICKED DEVICE(CUSTOM BINARY WAS BLOCKED BY FRP LOCK)!!!

If that happens, here is an official guide from the Samsung Kies Support Page :

IMPORTANT: You may need your device model name, S/N number, or IMEI number in order to proceed. This information can be found on the label underneath your device battery.

WARNING: This process permanently deletes all personal information from the device. The information will not be recoverable if you proceed with this process.

1. Open Kies 3 and click Tools > Firmware Upgrade and Initialization.

2. Enter your device Model name and click OK.

3. Enter the device S / N number and click OK.

4. Kies 3 will verify that the feature is available for your device. If the feature is available, click OK to continue.

5. The firmware version is displayed along with a note that the information on your device will be permanently deleted during this process. Click OK to continue.

6. Follow the steps to prepare your device for emergency recovery. Mark the checkbox next to I have read all of the above information. Select whether you agree to share this update with Samsung. Connect your device to Kies when you have activated the download mode. When your device is in download mode and connected to Kies 3, the Start upgrade button is available. Click Start upgrade to reinstall the firmware.

7. Touch Create backup to create a copy of selected items before proceeding. Touch Skip backup to proceed without backing up any items.

8. Kies 3 will download and prepare your system to update the firmware. This process can take some time. The time will vary based on your network and computer capabilities.

9. Respond to any security warnings about installing software.

10. The progress screen is shown during the upgrade process. The process will take several minutes to complete. Do not disconnect your device, turn the device off, or turn off your computer during this process.

11. Click OK when the upgrade is finished.

Therefore I provide you all the needed files to do this :

How to root SM-J320FN.rar