The accents are more important than any particular pattern.
Try hitting all downstrokes with accents on beats 2 and 4 at first (beats 1 and 3 should be bass notes but you can add that later). The upstrokes are just filler. Once you've nailed the song with solid downstrokes, your upstrokes will fall into place. Just keep listening to the song.
My advice is : don't get hung up on patterns.
