-style
way
fashion
Structure
- Noun + 風
- Noun1 + 風 + の* + Noun2
[Suffix added to nouns to express that something is in the noun’s style, has the noun’s outward appearance or noun’s tendency, etc.]
[Unlike みたい and よう, which are adjectives, 風 is used as a suffix to create a noun]
[*の can sometimes be omitted before a noun]
「このドレスは今風だと思ったら大間違いだ。」
“If you thought that this dress is in a modern style, then you were greatly mistaken.”
Given the だ in the beginning and at the end, shouldn’t the translation be in present tense?
“If you think¹ that this dress is in a modern style, then you are greatly mistaken.”
¹ More natural English should probably use present progessive (“are thinking”).