Where to find model # on free sewing machine

I assume you mean a Free Sewing Machine, antique.

From https://www.thesprucecrafts.com/sewing-machine-manuals-or-replacement-manuals-2978304

"The first step is finding your machine's manufacturer and model number. Most machines have a manufacturer's name somewhere on the machine. The model number may be on the back or bottom of the machine. If you cannot find a model number anywhere, take a photo of the machine and try emailing it to the manufacturer's customer service email address for help." Or, take it to the reference desk at your public library. They will do a search through print and internet sources.