It does not depend on the number of instruments you own. If, given the work you are doing with those instruments, it is clear that you need several (some sort of technical or artistic drawing, for instance), then when your words are to be understood in reference to this work, add an s. If it is clear that only one is needed, then use no s.

In your comment you are talking about

I haven’t used pens at all.

You could convey it with:

Je n’ai pas du tout utilisé de stylos.

Deepl is quite reliable for sentences like this.