To find the molarity given the molality and the density:
First, since you are given the molality, let's just assume that you are working with 1 kg of water as your solvent. Use this as a conversion factor to get moles of your solute:
1) Multiply both sides by kg to get moles.
2) Use Molar Mass of LiF to get grams
3) g solute + g solvent = grams solution
4) Find liters
5) Use your moles from #1 & your liters from #4 to get your molarity:
Hope that helps! Good luck!