I assume that you were not born in the United States, and that your mother was/is not a US citizen. If these assumptions are incorrect, the answer below does not apply.
A child born outside the United States to a US citizen and a non-US citizen will be a US citizen so long as the parent spent a certain amount of time physically present in the United States. For a child born before 1986 to gain US citizenship through a single parent, that parent would have had to spend 10 years total in the USA, of which at least 5 years were after the parent’s 14th birthday. So if your father was a citizen and lived in the US until at least 1966 or his 19th birthday (whichever was later), you would be a US citizen.
However, the document you describe does not prove that your father was a US citizen. Instead, it only proves that your father was admitted to the US as an permanent resident (a so-called “green card”). If your father did become a citizen, he would have received a Certificate of Naturalization. This would be necessary to prove your father’s US citizenship and, by extension, yours.
