const drive = DriveApp.getFolderById(`フォルダID);
drive.createFolder(`作成フォルダ名`);
const drive = DriveApp.getFolderById(folderId);
const folders = drive.getFolders();
let folder;
let flag = true;
while(folders.hasNext()){
if(folder.getName() === folderName){
flag = false;
break;
}
}
if(flag === true){
drive.createFolder(folderName);
}