A familiewapen is a family crest or coat of arms. Most people in the Netherlands did not have a coat of arms. People who used them were usually members of the nobility or other members of the upper class. Working class families did not have a use for a crest.
There are several heraldic databases and collections that will tell you whether a coat of arms exists for a particular name. Even if you find a crest for your name, that does not mean that your family ever had any right to use it, as there may have been several families with the same name. Only by doing genealogical research will you be able to prove that one of your ancestors used that crest. Typically, you would have to go back to the 1600s at least, since most crests fell into disuse after that.
See the Heraldische Databank [Heraldic database] to find out whether a coat of arms ever existed for your family name.