This is the 3868th most frequent Russian word.
афганистане
"Afганистане" translates to "Afghanistan" in English, specifically in the prepositional case, meaning "in Afghanistan."
In this sentence, 'Афганистане' is used to denote the location, Afghanistan, in the prepositional case, following the preposition 'в' to indicate where the mountains are located.
В Афганистане много красивых гор.
There are many beautiful mountains in Afghanistan.
Here, 'Афганистане' again denotes the location, Afghanistan, in the prepositional case, following 'в' to specify where the action of serving took place.
Мой брат служил в Афганистане три года.
My brother served in Afghanistan for three years.
In this example, 'Афганистане' in its prepositional case follows the preposition 'о' (meaning 'about') to indicate the topic of the discussion.