If you have recorded the data file with a wrong thermocouple type, there is no direct way to change the scaling.
The workaround is to use the reference curve. In the attahment is an example setup which shows, how is possible to convert from Thermocouple T type to thermocouple K type.
The setup can be modified, by using a different scale factors from the table which can be found here.
1. Use the time reference surve, to convert the temperature channel back to voltage.
2. Then use the second for converting the voltage back to temperature channel.