I was wondering about how to get the Txt file, and translating the game.
Any Unity game in particular? Depending on the game it can be straightforward or pretty cumbersome.
Some Unity games are translate-friendly by having the dialogues either exposed or neatly packed in an .asset file, while others have the strings hard-coded in them.
If it's the latter, some viable paths would be either
a) editing the .dlls by hand (pretty tedious), or
b) Using the awesome UnityInjector/Reipatcher combo which was initially developed for KiSS/Illusion Unity games, but was used e.g. in Glamour as well, though it requires some slight coding.