。
About twenty stalls lined up at the bazaar.
Literal
Arcade [at-には] approximately 20 [genitive-の] stalls [subject-が] lined-up.
勧工場 (かんこうば) is a specific term for a Meiji-era indoor bazaar or arcade — a precursor to the modern department store, where many small vendors shared a single space. An obsolete cultural concept useful for reading historical texts. 並ぶ ('to line up, be arranged in a row') is intransitive; its transitive pair is 並べる.