Connoisseurs, what the code is responsible for: echo "" | base64 -D > shadowhash?

Question

macOS

Full command description:

If you open the file in your favorite text editor, you will find some data under ShadowHashData. This is the hash data in Base64 format. Copy the data to your clipboard and convert it into another .plist XML file. Note, if you try to copy the data directly into the terminal, you will have problems with newlines, one solution is to copy the data into a text editor and manually remove the newlines .

echo "<hash data>" | base64 -D > shadowhash
file shadowhash
plutil -convert xml1 shadowhash

I can’t figure out how to enter this command into the terminal, what should I replace it with <"<hash data>"
. The terminal gives out some nonsense ,(