Hi Ramanajee,
Thank you for reaching the support. You could filter your report query with 'DISPLAY' type for campaign.advertising_channel_type to retrieve display only campaigns via API. Please find below the sample report query for reference. Let us know if you have any additional concerns.
SELECT campaign.id, campaign.name, campaign.advertising_channel_type FROM campaign WHERE campaign.advertising_channel_type = 'DISPLAY' LIMIT 100
Regards,
Nikisha Patel, Google Ads API Team