De or het usb-adaptertje?

The correct Dutch article is:

het usb-adaptertje

Rule Diminutives (-je, -tje, -pje): always het. See the rule
Meaning (Dutch) schrijfwijze voor USB-adaptertje

How to use usb-adaptertje

the usb-adaptertjehet usb-adaptertje
this usb-adaptertjedit usb-adaptertje
that usb-adaptertjedat usb-adaptertje
our usb-adaptertjeons usb-adaptertje
your usb-adaptertjejouw usb-adaptertje
every usb-adaptertjeelk usb-adaptertje
which usb-adaptertje?welk usb-adaptertje?
a big usb-adaptertje / the big usb-adaptertjeeen groot usb-adaptertje, het grote usb-adaptertje

Meaning, plural, diminutive, pronunciation and translations: WikiWoordenboek (Dutch Wiktionary) (CC BY-SA 4.0). Example sentences: Tatoeba (CC BY 2.0 FR).