First time trying to apply for Chinese visa

Hi, I was born in the United States in 1972. My parents became naturalized citizens of the US in 1977. When they received their citizenship they turned in their permanent resident (green) cards. Now I'm trying to apply for the Chinese visa for the first time. The consulate is asking for my parents green cards and Chinese passports. What if they don't have them anymore? Also my dad passed away in 2004, so I don't know if his documents exist anymore.