Assuming it’s Qantas points, you will need to find a oneworld or Qantas partner airline that services Tribhuvan Airport, as Qantas does not fly there. From a very quick search, one reasonable option I could find was Qatar Airways from Kathmandu > Doha > Frankfurt. Best way to search Qatar availability is using BA Executive Club search engine (create an account with a UK address). I have no idea when you want to fly, so don’t know if any seats are available. It would be ~78,000 points in business, or 42,000 points in economy (plus taxes). However, you will still need to call Qantas to book if you do find flights.
What are my options for a Qantas Classic Award redemption departing from Kathmandu?