That's impressive wait time! well, since your father sent out the I-130 when he was a US citizen it is incredible that he is still waiting for an approval. So with that said, HE need to call USCIS here is the link to the contact http://www.uscis.gov/about-us/contact-us/national-customer-service-center he should have received the Notice of Action after a month from the date he mailed out the I-130 petition. On that Notice of action, he was given a case number, that is the number he needs to check the status of his application. Do that immediately! it is the only wait to see what is going on! and you notify them of the dates! that it's been 42 months in process and that's just plain crazy!!!
Good Luck!!
According to the processing timelines for the California Service Center they were processing I-130 for Unmarried sons and daughters over 21 of US Citizens that were filed on May 28, 2010 on November 30, 2013.
Again since you are in a family preference category where only a certain number of visas are available every year, there is no rush to process your I-130. The best to do is follow the Visa Bulletin issued by the State Department and then once your preference category gets close to your I-130 filing date then I think you should start worrying. http://travel.state.gov/content/visas/english/law-and-policy/bulletin.html