well first of all your formula is n=m/M

n=number of moles

m=mass of substance

M=molar mass

after finding what the question is looking for you have to find the molar mass of your substance (in this case chloride) you have to look on the periodic table for that (molar mass is also called the mass number) after you have found your molar mass plug the numbers into your formula

n=0.274/(molar mass of substance, in this case chloride)

after you get your answer make sure you dont forget your units (mol or moles)

I hope this helps :)