Hey there @supritha.n welcome to the community!
I’m not aware of the search functionality working in the body of the request, but rather as params. In looking working with the Management API explorer documentation, the following query seems to work in my environment:
curl -L 'https://{YOUR_DOMAIN}.us.auth0.com/api/v2/users?fields=email&include_fields=true&q=email_verified%3Afalse' \
-H 'Accept: application/json' \
-H 'Authorization: Bearer {YOUR_MANAGEMENT_API_TOKEN}'