This article explains how to easily copy files from OneDrive to Box.
Excerpt
Log into O365 and open OneDrive. Select all with the radio button at the top, then select "Download."
Note
There is a maximum you can download at once, so if the download option does not show as pictured, you will need to select only some of your content in OneDrive.
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Select "Save File" then "OK." This process will take some time.
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Locate the file on your computer. Files are usually saved to your download folder or the desktop depending on your settings. Select the file, then right click, and select "Extract All..."
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Choose the location to save the folder then "Extract."