Where are the rocks on a moon rover stored? Some people say it's turned into powder.
And how do they collect the rocks from Mars?
At the moon, some powder (dust) was collected with the rocks, but the rocks themselves weren't turned into powder at the time.
Individual samples were stored in small sample bags ... Individual sample bags were collected into larger sample collection bags for transport back to the lunar module. These large bags could be attached to an astronaut's backpack (as shown here) or to the lunar rover. ... For return to Earth, the samples were stowed in storage boxes.
We haven't yet collected and retrieved rock samples from Mars. For now we use meteorites that originated from Mars and somehow got ejected from there and landed on Earth.