The first thing you need to do is find the formula weight for BaBr2. You can find the atomic weight (or mass) of each element in the periodic table. If you look up Ba (barium) you will see that it weighs 137.3 grams/mole, and Br (bromine) weighs 79.9 grams/mole. (I've seen variations in periodic tables, so if the weights in your table are a little off, don't worry about it.) Since there are 2 atoms of Br, multiply 79.9 x 2 = 159.8 . Add that to the weight of Ba: 137.3 + 159.8 = 297.1 g/mol . So 1 mole of BaBr2 is equal to 297.1 grams, which can be written as 297.1g/mol or mol/297.1g. Use whichever conversion works in the equation so that the proper units cancel out.
Now we can convert 10.65 grams to moles by using the g/mol conversion of BaBr2 :
10.65 g BaBr2 x (1 mole BaBr2 / 297.1 g BaBr2) = 0.036 mol BaBr2
The grams cancel out so we end up with moles of substance.
Use this method to answer the other question you posted.
Hope that helps.