as for milk; milk (with は marking it as the topic)
→ は
phraseUncommon#9,300
as for milk; milk (with は marking it as the topic)は is a topic particle placed after 牛乳 in natural Japanese, so the usual order is 牛乳は, not は牛乳. The exact sequence は牛乳 can occur when は follows another word, as in これは牛乳です。