Samsung Galaxy J3 Orbit
The latest firmware for Samsung Galaxy J3 Orbit (SM-S357BL) is S357BLUDS6BTE2 with Android 9, released on May 13, 2020 for 1 region (CSC). Every official firmware build for SM-S357BL, 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/S357BLUDS6BTE2
SM-S357BL started on Android 8 and has received 1 major Android upgrade; it now runs Android 9. The newest build, S357BLUDS6BTE2, was released on May 13, 2020. No new build has appeared for 78 months, so regular updates for this model have most likely ended.

SM-S741W

SM-S741B

SM-S947W

SM-S942W

SM-S942U

SM-S947U

SM-S948U

SM-S948W
The newest firmware for SM-S357BL runs Android 9: build S357BLUDS6BTE2, released on May 13, 2020.
The latest build for SM-S357BL, S357BLUDS6BTE2, was released on May 13, 2020 (6 years ago).
SM-S357BL has had no new firmware for 78 months, so regular updates have most likely ended.
Yes, all firmware files for SM-S357BL are 100% official, original, and obtained directly from Samsung servers.
To flash SM-S357BL, 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-S357BL.