The first sentence makes no sense at all, a kind of literally translation would be:
I find go the farm...
Auf
has several meanings, among them there are:
Some examples of this:
Auf dem Baum (in the tree)
auf der Erde (on earth)
auf dem Hügel (on the hill)
auf einem Pferd sitzen (to sit on/upon a horse)
warst du schon auf der Polizei? (have you already been to the police)
auf Gleis 3 (at platform 3)
auf Jamaika (in Jamaica)
auf dem Bauernhof (at the farm)
auf den Bauernhof (to the farm)
Prepositions in german are usually very difficult when learning. I recommend you to try to remember in which cases you use which preposition, it's a long way but with practice you will get better.
You use zu
to bind the verb, it's kind of the english to
:
Ich muss verstehen was ich lese, um es den anderen zu erklären (I have to understand what I'm reading in order to explain it to the others)