Download the Samsung firmware for the Galaxy J7 Duo SM-J727T with product code TMB from USA (T-Mobile). This firmware has version number PDA J727TUVS7BTC1 and CSC J727TTMB7BTC1. The operating system of this firmware is Android 8.1.0 , with build date Thu, 05 Mar 2020 06:57:54 +0000. Security patch date is 2020-03-01, with changelist 14133265.
AP (System &Recovery)
BL (Bootloader)
CP (Modem / Radio)
CSC_*** (Country / Region / Operator)
HOME_CSC_*** (Country / Region / Operator)
Other options in case first option did not work or isn't possible.
Option 2 VOLUME DOWN + VOLUME UP then USB cable
Option 3 POWER + VOLUME DOWN + VOLUME UP
Option 4 POWER + VOLUME DOWN + HOME BUTTON
Option 5 (Note9) USB cable + VOLUME DOWN + BIXBY
Option 6 (Note10) POWER + VOLUME UP
AP (System &Recovery)
Other options in case first option did not work or isn't possible.
Option 2 VOLUME DOWN + VOLUME UP then USB cable
Option 3 POWER + VOLUME DOWN + VOLUME UP
Option 4 POWER + VOLUME DOWN + HOME BUTTON
Option 5 (Note9) USB cable + VOLUME DOWN + BIXBY
Option 6 (Note10) POWER + VOLUME UP
For most devices, the model number (e.g. "GT-I9505" or "SM-G900F") is found inside the device. It becomes visible when you open your device and remove the battery.
As an alternative, you can also type your model name (e.g. "GALAXY S5") instead of the number. But it may be a bit more difficult to find your specific device that way.
Still not sure? Then perhaps Samsung can help you out with their model number lookup tool.