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).
In this sentence, 'उनके' is used to specify a recipient, formed in oblique case with the preposition 'के लिए'.
मैंने उनके लिए एक तोहफा खरीदा।
I bought a gift for them.
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'.