GraphQL query Parameters from Azure Synapse Pipeline

I am trying to extract and populate data into Azure Synapse Dedicated SQL pool from an API using ADF pipelines. I was able to implement the query without any parameters using the Copy activity, but I have been encountering issues while trying to add parameters. Most of the methods used till now throws the "InValid JSON error".

Below is the sample query. How can I pass a parameter successfully?

query( $createdAt: DateTimeString ){
  Trans( last: 10, filter: { CreatedAt_gte: $createdAt } ) {
    pageInfo {
      hasPreviousPage
      hasNextPage
    }
    edges {
      cursor
      node {
        invNumber
        subledgerId
        CreatedAt
        ModifiedAt
      }
    }
  }
}