i really don't know how i can thank you enough 还是i really don't know how can i thank you enough ?why?

i really don't know how i can thank you enough 还是i really don't know how can i thank you enough ?why?
i really don't know how i can thank you enough
还是i really don't know how can i thank you enough ?
why?

i really don't know how i can thank you enough 还是i really don't know how can i thank you enough ?why?
i really don't know how i can thank you enough
从句要用叙述形式

第一个,不是问句不用倒装的,

我认为是:
I really don't know how can i thank you enough
这是一个宾语从句吧,用陈述语气问

I really don't know how i can thank you enough
是这个，宾语从句的语序是正常语序