Convert usb scale output to serial
It is not a straight forward usb-cdc/virtual com port. The Scale uses a USB-HID slave/peripheral controller. This needs to be read using USB-HID. It is completely different from USB-CDC, a.k.a. a usb virtual com port. It does not use a USB to RS232/TTL adapter.

See http://steventsnyder.com/reading-a-dymo-usb-scale-using-python/ and https://stackoverflow.com/questions/1275974/program-for-hid-usb-scale and https://www.youtube.com/watch?v=srvtDNYR05U

Also, your idea of using a USB to Serial cable will not work that way. A USB to RS232 cable is not bi-directional. It can not be used in reverse. It will not connect to a USB peripheral/slave. It has to be connected to a USB host/master, like a computer.