"Vestidos para fiesta de noche" translates to "dresses for prom night." "Vestido" is the Spanish word for "dress," and "fiesta de noche" is the phrase that means "prom."
When translating this phrase, it's important not to translate word for word. "Vestidos para fiesta de noche," translated one word at a time, means "dresses for party of/about night." Additionally, if "fiesta de noche" is translated literally, it means "party of night." Relying on translators, such as Google Translate, can be misleading. Translated literally from one language to another can make it hard to understand how an entire phrase works as a whole.