Hello Harry,
You can't "convert" a file to a page, since a file can be anything from a Word document to a Powerpoint to a database.
If the file is something like a Word document, the closest you can do is open the file, then cut and paste the contents of the file into a page. However, that may not retain formatting, and it may not be possible to cut and paste from all file types.
If the file is something that can be displayed by the Canvas previewer (see What types of files can be previewed in Canvas? ), then you can also add a link to the file within the page, and set it to automatically open the previewer (https://community.canvaslms.com/docs/DOC-12868-415268090 )
Mike
