How to replace all Finder files with a placeholder file for each
Basically you want to find a bunch of files which are empty (have size 0 bytes) and then change their content to "This file is empty".

cd to/wherever/the/files/are
find . -type f -size 0 -print | while IFS= read -r line; do
    echo "This file is empty" &gt; "$line"
done


If instead you want to remove them, run

cd to/wherever/the/files/are
find . -type f -size 0 -delete