\(\mathrm{KMnO}_4\) is potassium tetraoxomanganate (VII).
The 'tetra oxo' indicates that four atoms of oxygen are there. The 'VII' in the name reflects the oxidation number of manganese in the compound.
\begin{array}{l}
\mathrm{KMnO}_4 \\
1+\mathrm{Mn}^2+(-2 \times 4)=0 \\
1+\mathrm{Mn}_2-8=0, \mathrm{Mn}-7=0 \\
\mathrm{Mn}=+7
\end{array}