"Eu am patru cutii colorate în ghiozdan."

Translation: I have four colored boxes in the schoolbag.

[Zuravliovaa]

Ghiozdan - Bookbag is the only option?

[Bart249088]

Sounds somewhat weird to me ... 'in the schoolbag'. Any native english speakers around?

[sakurasobakasu]

yep weird. at least 'in my schoolbag'...

[Hormazd9]

What is the difference between schoolbag and the schoolbag?

[-Afina-]

It's:
un ghiozdan
ghiozdanul
ghiozdane
ghiozdanele

Remember that you drop the article after a presposition as long as the noun is not further modified.
For it to read "in a schoolbag" it has to be "într-un ghiozdan".