@Kiki89, Welcome to English Stackexchange.
Your third sentence is the correct one. In the first example you cited above, the second comma is used where you might pause while reading the sentence.
Many writers have been told to use a comma anytime they would pause while reading a piece of writing. While following this suggestion will lead to correct comma usage in some situations, there are many other times when following this guideline will lead to unnecessary comma usage.
Use a comma to separate independent clauses linked with
coordinating conjunctions. If you have what can be two separate
sentences but want to make them one (creating a compound sentence),
use a comma and a coordinating conjunction (for, and, nor, but, or,
yet, so) to link them. (More information on compound sentences) The
comma should be placed in front of the coordinating conjunction.
My English Instructor was a good teacher, and he taught me a lot about
the writing process. We left the house later than we hoped, but we
still made it to the concert on time
In your second sentence, the comma should come before the 'and'.
Use a comma to set off nonessential elements. A nonessential element
is a word, phrase, or clause that is not needed to complete a
sentence. In other words, it can be removed and the sentence still
makes sense and is grammatically correct. If removing the element
changes the meaning of the sentence, it is essential. Nonessential
elements need to be offset with commas, both before and after.
Examples of nonessential elements:
I went to the movies with my neighbors, Ron and Sally, and then we
went to dinner. The students in my morning class, ENG 121, like to
participate in the discussions. Her best friend, Heather, is planning
a surprise party for her birthday.
Comma rules are explained here:
I hope this helps.