i don't know that where you are

这句话正确，这是个宾语从句。

语从句中that一般情况可省 ,但that在引导宾语从句时也并不是任何情况下都可以省略。在以下情况下，that不能省略。

1． Everybody could see what happened and that Tom was frightened.(and连接两个宾语从句，that宾语从句放在and的后面时，that不能省略。)

大家都会看出所发生的事情并知道Tom非常害怕。

2．I know nothing about him except that he is from the south.(that引导的宾语从句作介词宾语时，that不能省略。)

对他我一无所知，只知道他是南方人。

3．That he ever said such a thing I simply don’t believe. (that从句位于句首时，that不可省略。)

我简直不相信他曾说过这样的话。

4． We decided, in view of his special circumstances, that we would admit him for a probationary period. (主句谓语动词与that从句之间有插入语，that不可省略。)

i don't know that where you are
这句子不对。把that 省。一般后跟特殊疑问句不用that，一般疑问句用if /whether.陈述句用 that或不用均可。
我是从事英语的，乐意为你解答。

语从句中that一般情况可省 ,但that在引导宾语从句时也并不是任何情况下都可以省略。在以下情况下，that不能省略。