Best way to install O365 over old versions of Office and not lose anything?

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Facts: 

  1. My wife is the original purchaser of our O365 Home two years ago and installed it on her iMac.
  2. We then installed it on my Win 7 Pro 64-bit machine, so I am the next user of the five or six permitted total users.  We have also installed it on two iPads and an iPhone, which I understand do NOT count against the five or six permitted installations.
  3. Now - my wife also has a personal Win 7 Pro 64-bit machine for her SOHO use on which she has BOTH (a) Office 2003 32-bit with 2007 Compatibility Pack (installed in 2013) and (b) Excel 2013 32-bit (installed two years ago).
    On this machine, many documents are backed up using a SugarSync account.  As far as I know, OneDrive has never been used on this machine UNLESS there was a mandatory sign-up when we installed the Excel 2013 32-bit, in which case we forgot the user name and password.

Question:   On my wife's SOHO machine, what is the best way to install our O365 Home 64-bit so that NOTHING is lost - no Word or Excel files, no lists of recently opened documents, no links to where the existing files are -- NOTHING IS LOST and O365 works seamlessly with all these items available as if it had been there all along.

Please feel free to point me to good articles about this.

Again, we don't know whether we ever signed into OneDrive when we installed the Excel 2013, but I'm pretty sure it wasn't ever used.

Thanks.