There's not really a straightforward way to get metadata from an XMP file into a JPEG. You could load the XMP file into the Metadata Info window, but you'd need to do that for each image (or load it into the Metadata Template and apply the Template into selections of corresponding images).
I'm curious how the XMP files came to exist in the first place? I don't think I've ever seen the stock camera app create XMP files, I'd think that any application that was adding metadata would just embed it in the JPEG?