Were to look for model numbers on old singer sewing machines treadll models?

Most antique sewing machines do not display the model number anywhere on the machine. If the machine is made by Singer, you can cross the serial number to a model number and "birthdate" at singerco.com. If the machine is made by some other company, you will need to do some research. Needlebar.org has hundreds of photos of antique sewing machines and might be a good place to start looking.