I'm wondering how to ask a superior what the appropriate dress code is, for
example: "what is the _appropriate_ attire to wear on my first day? (of work
etc)."

Any help would be greatly appreciated! Thank you!
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2017-07-10T01:29:11.417
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question
words usage
Word for "appropriate" as in dress code etc
> Word for “appropriate” as in dress code etc.

How about [適切]{てきせつ}な, ふさわしい, as in 「適切な[服装]{ふくそう}」「ふさわしい服装」

> "what is the appropriate attire to wear on my first day? (of work etc)."

I would say:  
「[初日]{しょにち}はどんな服装が｛よい・よろしい・ふさわしい・適切｝でしょうか？」  
「初日はどんな服装で行けばよいでしょうか？」

In case you want to sound a bit more casual:  
「初日はどんな[格好]{かっこう}で行けばいいですか？」
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2017-07-10T01:58:29.800
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answer
If you are looking for the natural/formal way a Japanese person would ask it
would be:

> 服装{ふくそう}の[決まり]{きまり}はありますか？  
>  _fukusō no kimari wa arimasu ka_
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2019-01-03T16:23:23.513
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answer