Mn is in its +7 oxidation state
 
In KmnO4 the Mn atom is said to be d3s hybrid
						

							
It's d3s 
						

							
its sp3 hybrisation 
Mn in ground state d5s2
Mn in exited state d3(dxdydz) s1 p3
 d3(dxdydz) these will form pi bond and s & p involve in sigma 
so its sp3
						

							
The hybridisation of Manganese in KMnO4 is d3s. ... In KMnO4, only three of the five molecular orbitals are used for hybridisation are used for bonding which means that the four oxygen atoms contribute or donate electrons to 3 orbitals only
						

							
Sd3 or you can also say d3s.
Now the question arise in your mind that why not sp3. This explain on the basis of hybridisation . As d obitals are lower in energy than p orbitals (because inner d orbital is use and it mix with s orbital not outer p orbital) , so as you know whenever orbital mixing take place, they always try to mix with lower energy orbitals.
Thats why hybridisation is sd3/d3s.
						

							
Sd3 
youget this answer from coordination compound chapter of class 12
sinc e mn is in +7
hope this will help you