It is not possible to import Safari bookmarks. The data in Safari is not accessible by other applications. This is by design: otherwise applications would be able to look at your Safari browsing history.

You can import your Safari bookmarks via a different route, but you will have to own a Mac to do this. If you enable iCloud on both your iPhone and your Mac, you can sync your Safari bookmarks between your iPhone and your Mac.

Now if you also use Firefox on your Mac then you can go to Bookmarks -> Show All Bookmarks -> Import Bookmarks from Other Browser and import your synced Safari bookmarks into Firefox.

By setting up a Firefox Sync account, you can then sync your Bookmarks from Firefox on your Mac to Firefox on your iPhone.

Unfortunately there is no easier way.

What about on iPad? Can this be done for this device as prescribed above please?