I put "burial" but it was marked as incorrect. Is there another Danish word for "burial"?
That should be acceptable, too. Another, more posh, word you can use is (en) bisættelse.
It feels a bit strange (though not really wrong) to ask "when" here, because you already mention a more general timeframe (Monday). I'd be inclined to ask "[at] what time" (EN), "wie spät" (DE), "❤❤❤ laat" (NL), etc. Would the Danish version sound better with "hvad tid" here?
You can use both in Danish, it does not sound that strange in Danish to say, "hvornår er det på mandag?". To ask "hvad tid er det på mandag?" might be a little more efficient as you would expect a precise time as an answer. You can also use the verb 'at foregå' (=to take place), not to be confused with 'at forgå' (=to decay)
I would suggest that the burial is the act of putting the body in the ground and is only part of the funeral. The funeral involves the various rituals etc and includes the burial.