How do I recreate dng files after they were deleted?

Hopefully, you can find them using Time Machine IF you had that setup and the drive with the DNG's was setup for it. Or you had a backup. Otherwise, you're SOL.

See my reply in your other post, but if ALL original files are no longer available anywhere (including Trash and backups) then you can only create smaller JPGs by using a plugin to 'export' the previews.

Extract JPGs from Previews Plugin

EXTRACT JPGs FROM PREVIEWS

Deleted images should be found in the trash on your computer. You can restore them from the trash, and that will return them to the folder where they were located. However, it will be necessary for you to import them into Lghtroom again and perform all of the editing because when you delete them from Lightroom there is no longer a record of any of the work in the catalog. It will be necessary for you to do all the work again. Of course, if you have emptied the trash then the DNG files will be gone and there will be nothing for you to recover.