How do I retrieve contacts accidentally deleted

If you accidentally deleted your calendars, reminders, bookmarks, or contacts from iCloud, read this support article --> If you accidentally deleted your calendars, bookmarks, or contacts from iCloud - Apple Support

This article has similar information --> Restore contacts stored in iCloud on iCloud.com - Apple Support

If you do not use iCloud for Contacts you may be able to restore from a backup but that entails resetting your entire device back to the time you made the backup.

Read this document to discover how to restore your iPhone, iPad, or iPod touch from a backup --> Restore your iPhone, iPad, or iPod touch from a backup - Apple Support