Here's an example of what my .jpg files look like:

I want to append either the "Date" or "Date taken" info — not the "Date created" or "Date modified" info. I saw this answer but I think it would only do the latter. Also, I would like the date formatted as YYYYMMDD or YYYY-MM-DD, no times included. Can someone please help? I know enough python to run a script but definitely not enough to actually write or troubleshoot one. :\
If anyone knows how to do this in R, I'm much more comfortable there.
If I have understood your request correctly, please find below a proposed solution to your problem using the packages
exifrandstringr. With some adaptations for your specific case (i.e. file extension and path diretory), it should work.