@SachinKolekar Welcome to Microsoft Q & A Community Forum. You can enable the diagnostic logs for all the nics using Azure Policy service. For this, you need to create a custom policy definition which checks if the diagnostic logs are enabled or not. If enabled, the policy shows compliant. Ifs not enabled, the diagnostic settings are enabled automatically for new resources and for existing resources you need to create remediation task to deploy the diagnostic settings.
To create custom definition for enabling diagnostic settings for NIC within Azure policy, you can refer this document. To create remediation task for the custom policy, you can refer this document.