No no, the xBRZ isn't the right tool for upscaling these images.
You'll need to use XnConvert (free) to mass resize smooth images:
1. Get XnConvert: https://www.xnview.com/en/xnconvert/
2. Drag n drop you images into it.
3. In the 'Actions' tab, find the Add Actions>Image>Resize. Choose settings.
4. Check the 'Output' tab set up where to send the files, what format, etc.
5. Press 'Convert' button and it should be done.
Its worth mention that this process isn't perfect (it works somewhat but might result in some blurryness or artifacts). The future upcoming big overhaul of this pack will change this by making the default texture sizes to be natively 1024x1024 resolution.