Convert Existing Documents 

1.) Go to drive.google.com

2.) Select and open the document you want to convert within your drive

*If the document isn't in your Google Drive yet, please see the Upload Files to Google Drive article for instructions on how to do so 

3.) At the very top of the document, click the "Open with" button then choose "Google Docs" from the menu

4.) After a few moments the document will open into the GSuite version of itself (i.e. Docs, Sheets, Slides, etc.)

5.) Now if you go back to your Google Drive, you'll notice there are now 2 copies of the document

One is the original and one is the GSuite conversion

Tip: If you look at the icon next to the document name, you will be able to tell what type of document it is. 

For example, in the picture above:

The LEFT document is a Google Doc with the icon that has lines. 

The RIGHT document is a Microsoft Word document with a 'W' icon.