We have reviewed how to:
Upload files to your Google Drive
How to set up your drive so it will prompt you about converting files when you upload them.
However, there may be some situations in which you want to convert a file into a Google Document, Spreadsheet or Presentation that has already been uploaded to your Drive.
Fortunately, there is an easy way to convert files that are already in your Google Drive into one of the Google formats, allowing you to edit, collaborate and share. Here's how:
You can find more information about converting files to Google Documents, Spreadsheets and Presentations in the official Google Drive Help documentation at https://support.google.com/drive/answer/2407404?hl=en.
If you run into any issues when trying to convert a file, here is some information about the size limits, as well as other limitations, https://support.google.com/drive/answer/37603.