The sentence revision is: Nikita would like to know which car is theirs.
The possessive pronoun here is theirs.
Theirs replaces belongs to Yosef and Taiga.
Possessive pronouns help to show possession or ownership in a sentence. There are two types of possessive pronouns;
- the strong ( absolute ) possessive pronouns: mine, your, his, her, its, ours, yours and theirs. Their refer back to a noun already used replacing it to avoid repetition.
- the weak possessive pronouns : my, your, his, her, its, our, your, their. They function as determiners in front of the noun to to describe who something belongs to.