Anything downloaded from Safari on iPad will be found in your ‘downloads‘ folder in iCloud Drive. if not, check under Settings – Safari and see where you’ve specified files to be downloaded to.
So..
If you click save on a file on the web, and that file opens. Go to the share arrow on the top right and scroll down to save to files.
This will download the file and allow safari to be seen in the file permissions tab in settings as well