Which version of Pega are you on? In Pega 7.x versions, there is a REST wizard to guide you through the process of creating a REST connector. You could upload your JSON sample and the wizard would automatically create classes and properties to aid you in mapping your request parameters.
As a side note, your JSON is syntactically invalid. The values of "Branch" and "Track" fields must be enclosed within quotes if they are strings. You could use JSON validator such as http://jsonlint.com/ to validate your JSON.