To find the missing number \( x \) in the equation \( 390x = 390.000 \), we first need to understand what \( 390.000 \) represents in terms of powers of ten.
The expression \( 390.000 \) can be interpreted as:
\[ 390.000 = 390 \times 10^0 \]
The equation then becomes:
\[ 390x = 390 \times 10^0 \]
To solve for \( x \), we can divide both sides by 390 (assuming \( 390 \neq 0 \)):
\[ x = 10^0 \]
Since \( 10^0 = 1 \), we find that:
\[ x = 1 \]
Now, regarding the powers of ten mentioned (10^2, 10^3, 10^4, 10^5), these are just other forms of expressing numbers but don't change the value of \( x \) in this context.
Thus, the missing number \( x \) is:
\[ \boxed{1} \]