Kenmore sewing machine model numbers start with three digits. For example 117, 148, 158 or 385. This number is the manufacturer of the machine. After this prefix is the model number of the machine. You need both numbers to have the complete model number of your machine.
The model number will be on the machine either on a plate or engraved into the machine housing. Many older models the number is on the front bottom. If the machine is installed in a case you will have to tilt the machine back to see the model plate. The four digit model number on the motor of your machine is not the sewing machine model number. It is the model number of the motor. Below are some examples of where to find the model number.
Many different models use the same manual. For example model 158.14000, 158.14001, 158.14002 all use the same manual. 158.1400 is the primary model number. The last digit is when the machine was produced. There may be color changes or other minor changes but the base machine and functions are the same.