Google Apps Script doesn’t offer a method for moving files from one folder in Google Drive to another one but there’s an option to add a file in Drive to multiple folders (similar to symbolic links in Unix). That can be used for moving files as well - remove the file from all existing folders and add it to the target folder.

// Move file to another Google Drive Folder

function moveFileToAnotherFolder(fileID, targetFolderID) {
  var file = DriveApp.getFileById(fileID);

  // Remove the file from all parent folders
  var parents = file.getParents();
  while (parents.hasNext()) {
    var parent = parents.next();
    parent.removeFile(file);
  }

  DriveApp.getFolderById(targetFolderID).addFile(file);
}