I’m not sure that is it free?

i'm not sure that it is free 肯定句子.
无不确信那个是否免费
你是要改成疑问句吗?对 我是想要疑问句。就是想向对方确认某件事情。。。are you sure that is free ?你确定那是免费的吗？就完全可以了I want to make sure that I can cancel the “breakfast”,because I don’t think I really need it.那么这句这样说对不对呢 谢谢啦i want to make sure that whether i can canclethe “breakfast” or not, because I don’t think I really need it.或者 i want to make sure that if i can canclethe “breakfast” . because I don’t think I really need it.加一个"是否" 句子会更流畅谢whether 表示 “是否” 后面必须加 or notif 表示 “是否” 不用加这里加if是必须的吗？如果不加会不会有语法错误呢？whether of not 和if这两句哪个表达更好一些呢？谢啦