>>16810443so you're probably wondering where the 6 million figure came from, I'll bet. Luckily, I got you covered fren.
The Germans kept records. Names, dates of birth, cities of residence and birth, of everyone that died in the camps. That is how they knew to arrest them.
PROTIP: if you keep records because you are certain that you will win the war and the world will be on your side ... then you better win the war.