
Samsung Galaxy J3(2016)
The latest firmware for Samsung Galaxy J3(2016) (SM-J320N0) is J320N0KOU1AQK1 with Android 6.0.1 (Marshmallow), released on November 5, 2017 for 1 region (CSC). Every official firmware build for SM-J320N0, newest first: one row per build with all regions (CSC) that received it.
Each firmware build has its own page at https://samfirm.shop/build/{PDA}, where {PDA} is the build number from the list above. Example: https://samfirm.shop/build/J320N0KOU1AQK1
All 10 builds in our database run Android 6.0.1 (Marshmallow). The newest build, J320N0KOU1AQK1, was released on November 5, 2017. No new build has appeared for 109 months, so regular updates for this model have most likely ended.
Specifications of SM-J320F, a regional variant of the same device. Chipset and SIM lines are left out: they can differ by region.

SM-J320VPP

SM-J327VPP

SM-J326AZ

SM-J337A

SM-J330N
The newest firmware for SM-J320N0 runs Android 6.0.1 (Marshmallow): build J320N0KOU1AQK1, released on November 5, 2017.
The latest build for SM-J320N0, J320N0KOU1AQK1, was released on November 5, 2017 (8 years ago).
SM-J320N0 has had no new firmware for 109 months, so regular updates have most likely ended.
Yes, all firmware files for SM-J320N0 are 100% official, original, and obtained directly from Samsung servers.
To flash SM-J320N0, you need to download the appropriate firmware, put your device into Download Mode, and use the Odin tool to load the BL, AP, CP, and CSC files.
Downgrading is only possible if the bootloader version (binary bit) of the old firmware matches the current one. Always check the binary version before flashing SM-J320N0.