As you are re-using data from SRA, it might be easier to use q2-fondue, which will download, reformat, and import to QIIME 2 in a single step. See this tutorial (and please open a new topic if you run into issues using q2-fondue):
But otherwise you can use the "Manifest" format (see the QIIME 2 online documentation for a tutorial) to import the data that you have already downloaded.