I am filing for a cancer payout and need the citizenship records of my dead parents to prove they were both citizens of the united states but don't know where to look I went on some online sites and could not find anything

Are you in the US (hopefully) because you are probably going to have to go various places in person. Did they have Social Security numbers (they would if they worked or had Medicare, etc)? A Social Sec office would be a good start, but anywhere you go you will need proof of who you are and who they were. There are a lot of privacy rules for 70 years after someone dies. The funeral home will have SS numbers too.