Start here:
… Transfer photos and videos from your iPhone, iPad, or iPod touch to your Mac or PC
I’ll also mention a common source of confusion and trouble: that the date of file creation is not the date associated with the photo, and that the EXIF metadata stored within the photo has that and other details, where the file system metadata does not. Too many folks have gotten erroneously tied to the file system dates, and not to the EXIF metadata as is preferred and far more reliable.
Or… If you don’t want to use the existing Apple tools, such as Photos and iCloud Photos, and related:
… Transfer images in Image Capture on Mac - Apple Support
If you want to stay strictly on the iPhone device and not use iCloud Photos, and not use a Mac or Windows computer, that’s tougher… Here’s an earlier discussion of that:
… How to move Photos Out of Camera Roll? - Apple Community
Keeping photos entirely locally on an iPhone without remote backups or use of iCloud does mean the loss or theft or damage or dunking of an iPhone is a catastrophic loss of all photos, though.
And I’d suggest updating to iOS 15.4.1; to current.