"YOURS" in the sentence is a possessive pronoun because it is the possessive form of the pronoun "you."
Explanation:
Similar possessive pronouns are my, mine, ours, its, his, hers, theirs, etc. The difference between personal pronouns and possessive pronouns is that personal pronouns help us to avoid repeating the nouns, while possessive pronouns are used when it is not necessary to name the person who owns the thing.
