Hi JackB1
Here’s some useful links
To get your *.sng files into BBM, use the File > Import > Song menu. If a download is *.zip, it usually just means that other interesting files are included, such as a chord or lyric sheet. *.mid files are typically the original source midi file which was used in creating the *.sng file for use with the BB. It’s included in case you want to redo the conversion - for example you might want it in a different key.
If you see a *.pbf file (not a *.pdf) it’s a folder file (ie a collection of *.sng files) which is imported using File > Import > Folder menu.
In your example the zip includes a lyric and chord sheet pdf, the original midi file and several versions of the song. The __MACOSX folder is an artifact of the zip being created on a Mac computer, and can be safely ignored.
If you got the file from this post
the author has hinted at what’s included.