SCADA data is not from a SCADA instrument. It is poled from a collection of many instruments reporting what each instrument is measuring. There are a number of protocols that the instrument poling system can use, many proprietary, although at least one is open. The SCADA system is the integration of all the poled intrument values and time stamps of when measurements were taken into a presentation resulting in a display of the current state of the system understandable to the system's operator.
The data conversion will depend on which protocol is being used by the instruments and whatever format is required by the input to the "SCADA" program.
Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus