14 files declare their use of PluginBase in Backup and Migrate 5.0.x

CompressionFilter.php in src/Core/Filter/CompressionFilter.php

DatabaseSource.php in src/Core/Source/DatabaseSource.php

DBExcludeFilter.php in src/Core/Filter/DBExcludeFilter.php

DestinationBase.php in src/Core/Destination/DestinationBase.php

DrupalBrowserUploadDestination.php in src/Drupal/Destination/DrupalBrowserUploadDestination.php

DrupalEncrypt.php in src/Drupal/Filter/DrupalEncrypt.php

DrupalUtils.php in src/Drupal/Filter/DrupalUtils.php

FileDirectorySource.php in src/Core/Source/FileDirectorySource.php

FileExcludeFilter.php in src/Core/Filter/FileExcludeFilter.php

FileNamer.php in src/Core/Filter/FileNamer.php

MetadataWriter.php in src/Core/Filter/MetadataWriter.php

Notify.php in src/Core/Filter/Notify.php

SourceBase.php in src/Core/Source/SourceBase.php

StreamDestination.php in src/Core/Destination/StreamDestination.php