There isn't a single Hebrew word that directly translates to "la-nu" as it's presented. "La-nu" is a Hebrew prepositional phrase meaning "to us." The spelling depends on the context and the following word. To spell it correctly, you need the verb or noun it's modifying.
For example:
* תנו לנו (tenu lanu): Give *to us*. This is a common phrase.
Therefore, there's no single spelling for "la-nu" in Hebrew; it's always part of a larger phrase.