Hi Sandhya,
As of AEM Forms 6.2 release, you could pre-populate an adaptive form using XML data. If you have JSON data as per business requirements, you could convert the JSON data to XML data for pre-populating the form. If you wish to know more details on how pre-populating adaptive form fields work, you could refer to details at [1]
In 6.3 release, we are also planning to incorporate the notion of pre-populating adaptive form using JSON Data.
Thanks,
Rishi
[1] https://helpx.adobe.com/aem-forms/6-2/prepopulate-adaptive-form-fields.html