Compatibility of MSSQL to current releases

Unfortunately I do not have an identification on the MS SQL server version.  The developer, Scott Burris, originally designed a World War II Army Air Forces database back in 1998. His system was managed through his web hosting company.  About two years ago, the company dropped support of MS SQL.

I am the President of the Heritage League of the Second Air Division - USAAF, a non-profit organization dedicated to preserving the legacy of the fourteen B-24 Liberator bomb groups that were part of the Eighth Air Force.  What we're hoping to do is to preserve the almost 15GB of data that Scott's collected between 1998 and 2015.  We have several members of our executive staff that are familiar with relational databases using Apple's FileMaker Pro.

What we're hoping to accomplish is to convert the data in the MS SQL format into MySQL which our website hosting company provides.  Any suggestion or ideas would be greatly appreciated.