would someone please help me out with strumming please reply

Strumming is all about feel.  As soon as you lock yourself into a down up down up "pattern" you become mechanical and the song draws cold.  I'm assuming you're playing acoustic, so listen to Bobby D play knockin on heavens door, and try to strum along so it sounds the same.  Feel it out.  Both of those songs (assuming again you're playing an acoustic) have short G chords to start the progression.  Use a click or tap your foot as your starting out to keep time, but realize that the strum IS NOT a beat.  Don't think about strumming like down 1 up 2 down 3 up 4.... Every song is going to be different.  A lot of songs have a (or work with) the "pattern" of ddu udu udu udu.