A lot of people play this tune in the key of C and use a capo to play it in the key of D. Earl Scruggs often did this with tunes that are played in D major. Learn the melody in C and D to see how the shapes and patterns are similar and you will begin to gain a better understanding of the fretboard layout on the banjo.
Use the difficulty slider to reveal a barebones melody. This is still a great place to start and gives you great foundational understanding of the pitch movement in this melody.