How many nuclear power plants would we need to get us to 100%

[FBaggins]

12. Reconsider E = mc2

From what I've read there isn't enough known deposits to even get there. I may be wrong.

You are (though total electrification powered by nuclear is not a realistic scenario anyway). Remember that only the tiniest proportion of nuclear fuel is actually "burned" / converted to electricity. The reason the fuel needs to be replaced after a few years is that while the fission products are still a small proportion of the total mass, they impair the ongoing nuclear reaction. There's still lots of usable "fuel" in there... it just needs to be separated from the rest. The US doesn't see any need for that now because uranium is so plentiful and cheap... but if you increased the number of reactors tenfold (in a world market that is also many times larger)... then recycling would be prefered (as it is in other countries) to reduce waste (and waste storage) and dependence on foreign uranium supplies.

But as I implied in the earlier reply... fuel supplies in such a scenario really aren't a big concern. While thorium has some rabid fans, it isn't necessary in the current mix, but it certainly could become so if we thought that uranium supplies were in danger even after recycling. Or you could go with something like a traveling wave reactor that's fed with plutonium (recycled from spent nuclear fuel) that breeds depleted uranium into usable fuel. Even if uranium and thorium weren't plentiful... using depleted uranium makes the supply a multiple-century issue (by which time we had better have fusion licked)

Where would we get the water to cool them?

Not all cooling options consume large amounts of water. Proper siting of reactors needs to include water supply concerns. Additionally... I'm a fan of using waste heat from reactors to desalinate sea water. They could even help the water supply concerns.