There's a IC-world > IC²-World tool in the Add-On section.
Otherwise, IC1 worlds are NOT compatible with IC².
Though of course 1.7 IC² worlds are fully compatible with IC² of 1.8.1, you weren't exactly clear whether you meant this.
Well actually neither of those scenarios. I installed IC2, and I have an old save (a save from where no mods were installed. Not IC1, nothing)
Will I still need to create a new world or new save to find resources?