Translation:The tourist is looking for his passport in the backpack.
English just uses such possessives a lot more than Polish does. In Polish, you just assume that it is his passport, unless it's stated otherwise.
You can also just write 'a passport' or 'the passport', it's accepted.
So Paszportu is genitive and ends with a U, and plecaku is locative and ends with a u. Is Paszport male and plecaku female ?
In this place in the sentence it would be "her".
But anyway, "turysta" is a man. "turystka" is a woman.