How to retrieve deleted photos from iPhone?

They are stored in the Recently Deleted folder for 30 days in case you change your mind. If it has been longer then that or you have deleted them from your recently deleted folder, then you will not get them back. Note that when you delete from the recently deleted folder, you are met with a warning that continuing with that action will result in your photos being permanently deleted.

This support article details the process for doing it at iCloud.com.

Delete and recover photos and videos on iCloud.com - Apple Support

Read this support article for full information --> Delete photos on your iPhone or iPad - Apple Support

- "If you want to permanently delete your photos or videos, you can remove them from the Recently Deleted album. When you delete a photo from this album, you can't get it back."

"Permanently" means "permanently", with no chance of recovery. If you kept them on a separate backup device then have a look there.

This post by ASC contributor Lawrence Finch includes a list of places you can check where you may still have copies of photos.

Recovery permanent deleted photos - Apple Community