"I'm Yours" has a reggae feel to it. With reggae, typically the strong beats in the bar are 2 and 4, so a starting-point for the strum pattern could be --D---D-
Those beats are best clipped short, so a muting technique helps too - either chunk strum or fret-hand (or left-hand) damping for example. Personally I do that strum with chords a little up the neck so I can damp them with my fret hand.
A youtube search for "Reggae ukulele strums" should come up with some useful ideas for that song.
hth