How to tell which font a document uses
Open the document in Word, select some Nepali text and look at the font menu. If it says Kantipur, Sagarmatha, Himalb or Preeti, the text is stored as English characters and needs converting before you can use it on the web, in email or on a phone. If it says Mangal, Kalimati, Mukta or Noto, it is already Unicode.
Copy the text the right way
Select the text in Word and copy it normally. Paste it in the box above: the English-looking characters are what the converter needs. If you paste into a plain text editor first, nothing is lost.
Most documents use Preeti. For that, the Preeti to Unicode converter also gives you a preview and image export.