Blue Nancy Drew Mystery books

5 Nancy Drew books Gossett and Dunlap publishing by Carolyn Keene.
The Secret of the wooden door. Light blue cover. CR 1950. In good shape
The Secret at Shadow Ranch, Light blue cover CR 1931 Excellent shape
The Mystery at the ski Jump, Light blue cover, faded, torn from spine, Poor shape, CR 1952 Contents inside cover are all okay.
The Clue in the Jewel Box, Light blue cover, some staining on cover. CR. 1943
Nancy's Mysterious letter. Dark blue older book, spine boken and some fraying, contents good shape
CR. 1932.
I know these are worth something. We have more but these 5 are the oldest the others are the newer 1960 versions with colored pictures. Have several of them and hardy boy ones. My son wants to know what these might be worth. One book as I said is damaged but the other 4 are in good to excellent shape.