De or het potloodje?

The correct Dutch article is:

het potloodje

Rule Diminutives (-je, -tje, -pje): always het. See the rule

How to use potloodje

the potloodjehet potloodje
this potloodjedit potloodje
that potloodjedat potloodje
our potloodjeons potloodje
your potloodjejouw potloodje
every potloodjeelk potloodje
which potloodje?welk potloodje?
a big potloodje / the big potloodjeeen groot potloodje, het grote potloodje