> 6.7 million plates will probably weigh a lot. So off-world copies might need to use an alternative encoding scheme.
For the Moon and Mars, carve them into stone there. You'll have to defend against meteor strikes so they'll be carved and stored deep underground. No idea about seismic activity on those bodies.
For outer space, maybe it's pointless because finding, boarding, unloading an interstellar probe and sending the cargo back home is not easy unless you have very advanced interstellar ships. An orbit around the sun could be an easier place to spot. The Library of Ceres or the Library of the Troians?
But of course you need some marker then on the ground so people know where to look for it later if they want to read the data. Maybe some artwork? A giant monolith perhaps?
I'd start with the pyramid, but there's a risk of trying to dig up a regular mountain, which would be very wasteful. Maybe we should dig instead the Face of Mars after all, but who knows what other alien faces are there that we can't recognize? Let's dig everywhere!
For the Moon and Mars, carve them into stone there. You'll have to defend against meteor strikes so they'll be carved and stored deep underground. No idea about seismic activity on those bodies.
For outer space, maybe it's pointless because finding, boarding, unloading an interstellar probe and sending the cargo back home is not easy unless you have very advanced interstellar ships. An orbit around the sun could be an easier place to spot. The Library of Ceres or the Library of the Troians?