Hi Swapnil,
Can you confirm if you are using the AdWords API or AdWords Scripts? If you are using the AdWords API, the priority for campaigns is only available in shopping campaigns. There is no priority field for other campaign types such as search and display campaigns.
For the shopping campaigns, you can get the priority via the
campaignPriority field of your shopping campaign's
ShoppingSetting object. In the
CampaignService.get(), you can just include the
settings field in your selector, and it would automatically return the ShoppingSetting if your campaign is a shopping campaign.
Thanks,
Vincent
AdWords API Team