I deleted all my photo in my iphone how can i restore it

If you had iCloud Photo Library turned on, the photos would be in the Recently Deleted album for approximately 30 days and can be recovered from there either on the device or on iCloud.com.

If you didn't have iCloud Photo Library turned on but do have a backup from when the photos were on the phone, you can restore the backup. Note that the restore will replace all of the data (not just photos) currently on your phone with the data from the backup. See: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support