may be It can say: There aren't any pens left much is for uncountable noun and pen is countable noun.

"There are not MANY pens left" would be correct. 1. MUCH= quantity of uncountable noun/ verb (There is not much milk left. He doesn't talk much., etc.) 2. MANY= quantity of countable noun (She has many friends. We have gone to the park many times., etc.)