Where can you define Min and Max scaling values for the SCALING block in Unity Pro?

This is accomplished using the PARA input pin. You create a Derived Data Type variable of Type Para_SCALING and define the values within.
In order to see the variable listed in the Data Editor, make sure that the DDT box is checked as below.

Some related info on the other parameters.
The out_min and out_max will set the scaled engineering output. In the above example, entering 0-32000 will output a scaled 0-4095.
Clip can be used to limit the output to the out_min and out_max settings. In the above example if a value higher than 32000 is read, the output will go higher than 4095.
If the clip is set to true, then the output would set at 4095 and the status word will provide a value of 16 informing you that one of your input ranges have been exceeded.