Why did the pigs want to move into the farm?? I read chapter 5/6 and didnt find the anwser.
The pigs have to move into the farmhouse to fulfill the allegory that is Animal Farm. After the Russian Revolution when Joseph Stalin took over, he eventually became that which the Russians did not want and that which the previously ruling Romanov family was; tyrannical. This is a step in the process, occupying the symbolic place of mastery on the farm. As you continue in the novel, you will see further examples of changing the rules for Napoleon to better be able to be a dictator. A dictator however never outrightly tells his people he is being a dictator.
Thus, Napoleon made excuses for their needs to be able to do the brainpower of the farm. This move had to take place to separate the little people (or animals) from the dictator.
I assume you are asking why the pigs want to move into the farmhouse, as they do in Chapter 6.
Squealer gives two "official" reasons for this move. First, he says that the pigs need to be sure to have a good rest so that they can take care of the important business of the farm. Second, he says that Napoleon is too important to sleep in a barn or a pigsty -- he needs something more dignified.
In my opinion, the pigs are really moving into the house because they want to be more comfortable. They want things better than the other animals have them because they think they are superior.