Using adverbs - their proper order

[Melissa]

Hello. Could you tell me what the rules are for the proper placement of adverbs in a sentence? My 7th grader is on lesson XXII of LCII and wrote the following translation for "The citizens seek peace, however the generals prepare war."

Cives pacem petunt, autem, imperatores bellum parant.

The answer key has autem after imperatores. Is it correct either way or does it matter where the adverb goes? He wrote his translation in the order it was in English and I didn't see any rules or direction in the lesson plan regarding the placement of adverbs so I don't know how to explain to him the difference between the answer key's answer vs. his answer.

Thanks for your help! Melissa