Use Google's native Word workflow first
Upload your DOCX to Google Drive and open it with Google Docs. Office editing can keep the file in Word format; opening it is not proof that you created a native Google document. Use Google's conversion option if you need a Google Docs copy. Google distinguishes Office editing from conversion, and provides import instructions. Review the result after conversion.
Optional: produce a local Markdown copy
Upload your DOCX to the Word to Markdown panel, sign in and convert using credits. Download the .md file and compare its text, headings, lists and tables with the Word document. Your plan sets the upload limit. This step does not create a file in Drive or require access to your Google account.
Move checked Markdown into Google Docs yourself
For a file you want to edit in Docs, upload the .md to Drive and open it in Google Docs. Google's Markdown editing instructions explain that it stays an .md file. To insert its content into an existing Google document instead, enable Markdown under Tools > Preferences, copy the text, then right-click and choose Paste from Markdown. Ordinary paste is not the same command. See Google's current Markdown help.
Choose the route for the document you need
Use the direct Google route when collaboration in Docs is the goal. Keep Markdown when you need a text file you can inspect or use in a destination that supports its syntax. An extra conversion can change content or structure; it does not guarantee better fidelity. Check required tables, images, equations and review annotations, and retain the original Word file when layout matters.