SolidWorks File Version upgrade without PDM

So I've got a large directory of 400,000 SolidWorks files built over the years. Some are back to version 2005 in fact. We haven't touched them in years. We are getting ready to move them into a non-Dassault PDM and it's recommended that we update about 3500 of the oldest files to version 2018 (the SW release we are on).

I know I can do this fairly easily in a SolidWorks PDM environment, but what's the process for updating a single SolidWorks file outside of PDM?

Does anyone have a script to process 3500 files in this way? I can write one myself of course but figured somebody else already has. 

Thanks in advance. 

SolidworksAdministration