Notepad++ convert to UTF-8 multiple files

Here is what worked for me:

Go to Notepad++ -> Plugins -> Plugins Admin.

Find and install Python Script plugin.

Create new python script with Plugins -> Python Script -> New script.

Insert this code into your script:

import os;
import sys;
filePathSrc="C:\\Users\\YourUsername\\Desktop\\txtFolder"
for root, dirs, files in os.walk(filePathSrc):
    for fn in files:
      if fn[-4:] == '.txt' or fn[-4:] == '.csv':
        notepad.open(root + "\\" + fn)
        console.write(root + "\\" + fn + "\r\n")
        notepad.runMenuCommand("Encoding", "Convert to UTF-8")
        notepad.save()
        notepad.close()

Replace C:\\Users\\YourUsername\\Desktop\\txtFolder with path to your Windows folder where your files are.

Script works with .txt and .csv files and ignores all other files in folder.

Run script with Plugins -> Python Scripts -> Scripts -> name of your script

Got my mistake. My notepad is in german. So take care if it's called "Encoding" or in my case "Kodierung" and "Convert to UTF-8 without BOM" is "Konvertiere zu UTF-8 ohne BOM"

That helped me out!