Though maybe not on stone.
When I think about this question I think about how no one today can read the Inca's quipu and how it required the rosetta stone to translate Hieroglypics because the knowledge had been lost.
Therefore I think the best way to preserve vital knowledge would be in a form that was interlinear with multiple texts to multiply the chances that there will be a language known to the future people on there. Maybe a visual dictionary too. Language is a code and we need to make sure future codebreakers can find the key.
As to material - I'd say strong and durable not prone to break or decay. Stone, metal or plastic might all do.
Where? There should be multiple repositories around the globe. We don't know where civilization might re-emerge.
Becka