Hi, how to update existing dashboard templates from insights to new API ?
Hi @Pravin.Nemade,
Welcome to the Community 
In order to transition from the Insights API to the new Dashboards API, please see our migration guide => Dashboard API migration: from Insights API to NerdGraph
To read more about the transition and the how the improvements provide a better experience, I encourage you to check out Transition to New Relic One from Insights
Please let me know if you have any questions!