Hcfyk

I have a land card, for example Stone Quarry which reads "T: Add R or W." Do I take the mana from my library or my hand?

You are confusing Lands with Mana, a common beginners' mistake.

Mana is a resource that you use to cast spells; it is not represented by cards; you can not physically see it. When you tap a land, such as a Mountain, you add a red mana to your mana pool, which means you now have 1 red mana to spend.

When you tap a Stone Quarry, you choose to either add a red mana to your mana pool, or to add a white mana to your mana pool. Either way you end up with 1 mana in your mana pool. You do not get any land cards from your library or your hand.

Note that tapping a Stone Quarry is very similar to tapping a Mountain. When you tap a Mountain, you are activating an ability that says ""T:Add R." This ability is just not printed on the card for basic lands; it is instead within the rulebook for all basic lands.

An effect that has you put a land card from your hand or library onto the battlefield would specifically say so:

Arid Mesa's ability says:

Search your library for a Mountain or Plains card, put it onto the battlefield, then shuffle your library.

and Terrain Generator's ability says

You may put a basic land card from your hand onto the battlefield tapped.

Note that Arid Mesa can't even produce mana, even though it is a land. Lands commonly produce mana, but not all of them do.

Take a look at the old mountains, they had written on them "T: Add R to your mana pool" from 6th edition on they stopped printing that on the card itself, but the rules still include that all lands with the type Mountain tap for R, that's all the land does is add red mana when tapped. Lands produce mana, they aren't actually mana themselves. This is covered in the Comprehensive Rules(emphasis mine):

305.6 The basic land types are Plains, Island, Swamp, Mountain, and Forest. If an object uses the words "basic land type," it's referring to one of these subtypes. A land with a basic land type has the intrinsic ability "T: Add [mana symbol]," even if the text box doesn't actually contain that text or the object has no text box. For Plains, [mana symbol] is W; for Islands, U; for Swamps, B; for Mountains, R; and for Forests, G. See rule 107.4a. See also rule 605, "Mana Abilities."

That's also why the ability to add mana is in brackets on the more recent printings of typed duals like Sacred Foundry because being a mountain and a plains means it can tap for red or for white, it doesn't need to be explicit on the card, anything in brackets is just there as a reminder.