Most law firms have a style that they like to follow. You could ask them if they have a firm template they’d like you to match. If they don’t, I’d next ask them to specify which of the documents should be used as the format sample to match.
From there what you do next should really depend on the state of format sample to match. If it is formatted in a correct and stable way, from the perspective of proper use of Word, then you could just make a copy of that document, select all in it, delete, and save that blank document as your template. If it’s formatted correctly, then it should have all the styles you need to complete the task.
Converting footnotes to endnotes is easy. There is a built in function to do this on the References tab. Just click the little arrow button under the options for footnotes and endnotes to open the options menu for them, and you’ll see the option there.
If I’m not mistaken, though, I think they may be asking you to do something that is outside the scope of what a copy editor does. Your expertise is likely in language, and what they are asking requires knowledge of software. If you are not familiar with how to use Word to properly format and style documents the way they are requesting, I suggest explaining exactly what your area of expertise is and asking if their firm has a document processing department.
I have worked as a Legal Document Processor for law firms doing exactly what they are asking of you. Copy editing and proofreading are quite separate and distinct from the task you are describing.
