From where i can get image from user dropbox and display on browser

The /2/files/download endpoint is the correct way to retrieve the original file data for a file in the connected user's account. The response is the raw file data itself. You can use that however you want, e.g., save it to your server and serve it back to the user in your web app. If you don't want or need the original file data (the full image quality), you can use /2/files/get_thumbnail instead, which works the same way.