Hello Thanseer,
the simplest is, you ignore the files. These are 'backup' copies of the corresponding files before the files were overwritten by a newer version. The idea behind the 'bak' files (or folders): if you modify accidentally a project and you save this modification, the bak-files can be used to restore the previous version. Since everyone uses a version control system these days, the 'bak' files (or folders) have no importance anymore.
Best regards
Paul Banach