Correct is what works for you and feels the best.
There are certainly more efficient ways of course.
I generally try different things on more difficult bits to see what feels best.
In general, the closest finger to the target makes the most sense, but, you have to look to see where you are headed next too.
Since this song sits mainly on the 3rd and 5th fret, you can try (on 3rd and 5th respectively)
- Index / Ring
- Index / Pinky
- Index Pinky+Ring (comes from the Smandl technique, the ring finger helps out the pinky if not very strong)
I just looked back at my cover of this and I did something completely different, using index for most notes. It worked, but now that I have been playing a bit more I am inclined to do it the Smandl way above (but only becuase I have been working on this in private lessons).
So back to … whatever works!
It is slow enough and simple enough that it probably doesn’t really matter how efficient you are.
You can see how a bunch of folks did it here…