Trasposing from trumpet to Baritone Horn/ Pure Bass Clef / Low Brass Score of Hikari (Kingdom Hearts)

I am recently trying to find scores of the Kingdom hearts song Hikari, as I need one to play for a special occasion. Ones exist but do not have the melody in bass clef or low brass but instead trumpet flute lr clarinet. I need hell transposing it into trombone / Baritone Horn notes,or creating a whole new score which has the either the Trombone or Baritone Horn as the melody. I really need help, I dont know how to transpose and I cant write my own score because im a mobile user only. If someone could offer me something please tell me. I need it.