After doing more research on this subject, I think there are 2 methods of doing it.
1. upgrade from 12.1.3 to 12.2.0 (US) to 12.2.8(US) then use (Doc ID: 252422.1). Requesting Translation Synchronization Patches to request a translation synchronization patch for each language.
2. upgrade from 12.1.3 to 12.2.0 (US), applying all (12.2.0) NLS patches here then upgrade to 12.2.8 then again applying all (12.2.8) NLS patches here
but because this is an upgrade so we need to use Doc ID: 252422.1 to request a translation synchronization patch for each language again.
The difference between these 2 methods is file size. for method 1, it will be very large and method 2 is small.
I'll use method 1 for my upgrade.