Split every line in notepad.

We can't answer that - the chances are that when you converted your document, you discarded the line breaks, or assumed that Word text "broke" a line at the right edge of the page - it doesn't, those are "virtual lines" which only occur when formatting the document for the screen or printer. They do not exist in the DOCX file because the position of such breaks is dependant on the layout: flowing round images, or different font sizes for example.

If you want line breaks in your text version, you will have to work out where they should be manually, or by "line length" in the text file yourself (within the paragraphs of text from Word).