Hello Harisankar,
You have to filter the
criteria type with INCOME_RANGE to get the criterion related to the income range. You can use
Criteria Performance Report which provides statistics aggregated at the ad group criteria level. The sample program to download a report is
here, you can modify the report query as per you need.
If you strictly want to use AdGroup criterion service to get income range criterion then you have to change the service and selector values in
this sample code used to get AdGroups.
Regards,
Sai Teja, Google Ads API Team

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