Platteford Cemetery is in Sarpy County. Much of the land around it has been built with big houses, and it's tough today to figure out where it might be. Probably under a heavy canopy of trees. I've circled the spot where 194th and Sack Road would be in the aerial photo below; the graveyard is likely in the heavy foliage off to the left in the photo.
Visit the Sarpy County website's page on Platteford Cemetery.