Hi Mohanraj,
You may also check if you can form a custom JSON request having the above field inputted to JSON request file and you can use it to invoke the REST API.
However, the above is determine if your REST API accept same (however it is just standards).
Second way I can suggest beside suggestion by Yas, which may require a manual intervention is you can use action "user input- stop for manual operation" in which you can display the value of parameter and on accepting the same it will be following over to the REST call action, passing same.
Regards,
Saurabh