LME is about 10% heavier than the same amount of sugar's worth of DME; so you can divide by 1.1 to convert from LME to DME. If your LME can is 3.3 lbs, use 3 lbs of DME, for example.
As for what kind, I know there are dark DMEs available, but at my LHBS they only have the pale stuff from...