After importing my photographs in lightroom classic, I noticed in the metadata tab on the library screen- that the "date created" box has an incorrect date pre-filled. How do I adjust all the pictures in a collection folder so that the "date created" box has the correct image capture date of these images already imported?
Creation" and "Modification" dates bear no relationship whatsoever to the image "Capture" date, aka "Date Time Original". The first two are dates (and times) created by the Operating System, and reflect the time that the actual file was written to disk, and was last modified. Initially these two dates will be identical. The "Capture" date is created in camera and stays in the Exif part of the file header on your original files, and is also included on a derivative file (e.g. a jpeg export) unle...
"the metadata tab on the library screen- that the "date created" box has an incorrect date pre-filled."
LR (at least in English) has no metadata field labeled "date created". Are you referring to Capture Date? There are many different date fields with different meanings, confusingly named and mostly misinterpreted by users, so it's crucial to know precisely to which field you're referring.
If you really mean Capture Date, then as described in the articles linked to by GoldingD, you can use the Metadata > Edit Capture Time command.