This is the 51st most frequent Hindi word.
उनक
The word "उनक" appears to be incomplete or possibly a typo. It might be intended as "उनका," which means "his," "her," or "their" (possessive).
Here, 'उनके' is in oblique case, and is used to suggest possession when combined with a postposition like 'पास'.
उनके पास एक किताब है।
They have a book.
In this sentence, the word 'उनका' is a possessive pronoun used to indicate possession or belonging, implying the house belongs to 'them'.
उनका घर बहुत सुंदर है।
Their house is very beautiful.
In this sentence, 'उनके' is used to specify a recipient, formed in oblique case with the preposition 'के लिए'.