How do I recover deleted photos and videos on my iPhone ?

They will remain in your Recently Deleted folder for 30 days in case you change your mind. If it has been longer than 30 days or you deleted them from this folder also, then they are gone for good. When deleting photos from the recently deleted folder, you are met with a warning that continuing with that action will result in the photos/videos being permanently deleted. If you continue, then it will do exactly what it says

To check your Recently Deleted folder, you can follow the steps provided in this Support Article:

If you're missing photos or videos in the Photos app - Apple Support