Have a look at your help-file in MP3Tag (F1) at the section "Export".
https://docs.mp3tag.de/export
Short explanation:
Copy the code to the clipboard.
In MP3Tag goto File->Export-Button for new export file
Give the nerw file a name, e.g.: Count my albums, o.k.
Paste the code
Change the path in the first line to an existing path in your environment
Save the code
Goto File->Export and start your new created export file out of the list you see
More settings and explanations for export are in the help.
LyricsLover's example for the export file ist much simpler code and concentrates on album-name and counting.