ülkelerinin
"ülkelerinin" is a Turkish word. It is the genitive plural form of the word "ülke", which means "country" or "nation". Therefore, "ülkelerinin" translates to "of their countries" or "of the countries".
This word would be used in sentences where possession or belonging to multiple countries is being indicated.
The grammatical function of "ülkelerinin" is to show that something belongs to or is associated with more