string rootFolderPath = @"\\server01\Report\queue\;

string destinationPath = @"\\server01\Report\Output\";

string filesToDelete = @"*.bt";  

string[] fileList = System.IO.Directory.GetFiles(rootFolderPath, filesToDelete);

foreach (string file in fileList)

{

    string moveTo = Path.Combine(destinationPath, Path.GetFileName(file));

    System.IO.File.Move(file, moveTo);

}