Rashmi, it's quite easy to convert a Json String into a Json Object using UiPath. Just follow the below mentioned steps:
1. Create a new Process and go to Manage Packages. Search for UiPath.Web.Activities package in Official section and install it by clicking on Save.
2. Now drag Deserialize JSON activity and mention the JSON string you wish to convert into Object.
3. Store the output of Deserialization into outputJSON, a JObject type variable.
And you have your JSON object.