Does this work despite having the "Quarry" Mod?
I was looking for something to make my uranium ore more accessible since all my deposits are depleted now and new ones are a million tiles away from HQ and are only 10K to 100K in richness.
Will Deep Core mining work on already depleted deposits if just adding the mod now?

Hello, the quarry mod should not conflict with deep core.
For already depleted ore field unfortunatly there is no way to detect them afterwars as far as I know so this mod can't spawn them.
However you can spawn a few manually in your existing empty outposts with this command :

/c game.player.surface.create_entity({name = "coal-patch", amount = math.random(60000, 300000), position = {game.player.position.x, game.player.position.y}, force = game.forces.neutral})

Replace coal-patch by iron-ore-patch or copper-ore-patch depending on your need. It will spawn one deep core patch on your character position.

Also deep core does't support uranium for now (it feels there's usually way more than enough on the map, but it depends on map settings of course). Deep core may support it in the futur but it's more complicated because of required sulfure fluid.
In the mean time you could try the asteroid mining mod that provide some uranium but it is very endgame. (also doesn't quary support uranium ? Maybe different versions of it around).