I am living in the U.S. since March, 2009. In November 12, 2009 I got my permanent resident card. I am a retired teacher from abroad. I receive from my country an old age pension of $750 monthly, which I get here in the US using my ATM card. I need to know what form should I use and how to fill it out. Thank you very much.

If you were not exempt from residency up to Nov 12, 2009, you will file resident tax return for 2009, and report your worldwide income for 2009. Even pension income is taxable in the U.S.
If you paid taxes in the foreign country, you will claim credit for taxes paid in the foreign country by filing Form 1116. Your U.S. Tax Return: U.S. Citizen or Resident with Foreign Income