...wie x bestimmt schreiben wollte ;-)

or simply "ten to the negative six"

uh huu Thats the only thing which is right! MINUS (de) is always NEGATIVE (en)

aehe-be careful when you use the word 'always'.

The only way I would say this, is what BA said, namely:

"ten to the minus 6"

I would understand and accept some of the other formulations, but I would not use them, personally. So

> MINUS (de) is always NEGATIVE (en)

is not a true statement.

In the US "ten to the minus six" is by far the most common way to say this.
"ten to the negative six" is a bit odd.