You've inherited, or found at a garage sale, a Sears all-metal, model 158_______, sewing machine made in Japan. This machine sews through silk, cotton, denim, duck, sometimes even wood. No, just kidding.
Anyway, it's a great machine, but you don't have an electric chord or foot control. Voila! Your troubles are over! Here's a working one.
Be sure to note if your sewing machine has the configuration of two prongs close and one a separate so it will fit this electric cord. There will be another photo showing this.