Shrinking mdf files - SQL Server 2012
No, shrinking a file or a database never deletes data, at least not data that hasn't been marked to be deleted via the DELETE FROM or the TRUNCATE TABLE ... T-SQL statements.

The "Reorganize pages before releasing unused space" provides the facility to move data around within the file to allow shrinking the file as much as physically possible.  If the minimum size reported by the "shrink file" dialog is 350,000 MB, then you won't be able to shrink the file to anything less than that number.

You may want to look at this question and the associated answers for more details about the pros-and-cons of shrinking databases/files.