if you start with 5.5grams of magnesium chloride,how many grams of magnesium flouride will be produced?

I suppose I could ask what you are reacting MgCl2 with but I won't. You must have the right materials to make it work.

How many moles MgCl2 do you have?
5.5 grams/molar mass MgCl2.
1 moles MgCl2 is equivalent to 1 mole MgF2; therefore, moles MgF2 = moles MgCl2.
grams MgF2 = moles MgF2 x molar mass MgF2.