Hi. I am very inexperienced with MP3TAG, but I'd like to change the ITUNESCATALOGID. The problem I'm having is I don't know where to find the correct ID for my specific song. Is there some way to retrieve this?

How do you know that it is not the correct id?
How will you know that a track that got an id in Itunes is the same as your's?
AFAIK there is no script that retrieves that piece of information.

If you already know what needs to be corrected for your tags, why not do this yourself? You will spend far more time searching for the iTunesID you want, and end up with the same tag details anyhow.

you can very easily get the correct IDs using a web source, you can use either Apple Music or iTunes source both found in the web sources section