Hello divakar128,
Thank you for posting in the Apple Support Communities. We're here to help with your new iPhone.
From our understanding, you're missing contacts even though you've signed in to your Apple ID on the new iPhone. If you sync contacts to iCloud, make sure iCloud Contacts is green/enabled in the Settings app. If it is but you still don't see your contacts, consider whether they can be restored. Here's how:
Set up and use iCloud Contacts
Restore contacts stored in iCloud on iCloud.com
On the other hand, if you use a third-party email account (i.e. Outlook, Gmail, AOL, etc.) to sync contacts to your iPhone, we suggest logging in to the web version of that account to see if the contacts are found there. If they are, you can manually add them to the Contacts app or sync contacts to your iPhone again. To sync them back to your device from the email account, tap on Settings > Contacts > Accounts > [account name] > Contacts.
If iCloud Contacts wasn’t used, check for an iOS backup made before the contacts went missing. You can then restore from that backup and retrieve the missing contacts. Keep in mind that if you restore a previous iOS backup to your iPhone, any new information saved to your device since the backup was created might not be included.
Locate backups of your iPhone, iPad, and iPod touch
If a backup is found, restore from it using these steps:
Restore your iPhone, iPad, or iPod touch from a backup
We hope this information is useful. Kind regards.