I'm a bit puzzled by this. Photos should be in the Pictures library. In desktop view, click bottom left to open libraries and then photos. Are the photos duplicated in that?
I'm not sure what you mean by File folder? I think you mean file explorer.
Windows + F opens search.
I hope that all photos are back-up before deleting.
If duplicates are present in the photos library then it should be possible to select each duplicate by pressing ctrl and left click and then click on the delete icon or press the delete button.