You mean for your browser (whichever browser you use)? Probably in /data/data/<your-browser-app>, like all internal app data. You need root to view that directly. Some might keep them in a folder in /sdcard, but most don't.
See if your browser has an option to back up bookmarks or settings, though these days they mostly seem to prefer to sync them with their servers (they say "between your devices", but that's what it means in reality).