Hi Surabhi,
To go from a string to an enumeration, you would have to build a microflow (or nanoflow, depending on your use case) which evaluates the string and return the desired enumeration value based on the given string value
It can be far easier. In the community commons you have the action EnumerationFromString. Make a copy of the Java action move it to your own module and change the enumeration to the correct one.
Regards,
Ronald