A stock solution is a concentrated solution that you prepare for later dilution. There are a number of reasons for this. A substance may not be very soluble in water, you'd need say a 0.01 M solution, but you'd never be sure that tiny amount dissolved. You'd prepare a 0.1 M solution in alcohol or other solvent, then dilute in water.
Even if a substance is somewhat soluble, you wouldn't be sure a small amount was well mixed in a large volume. So you'd prepare a somewhat more concentrated stock solution, then dilute for working solution.
Like everyone else said, your protocol should tell you what the stock solution concentration should be, unless they've told you elsewhere, or expect you to ask some local expert, check the flasks in the lab for what's written on them, check published literature, etc.
We can't just suggest 0.1 M or 1 M for a stock solution, because don't know how soluble your solids are, how stable they are in concentrated or dilute solution, or what your application is.