These songs in their most basic form can be played in a Major key, the only minors will be when the song lands on one of the minor notes.
Let me explain a little theory. (We'll use C as an example)
C D E F G A B
1 2 3 4 5 6 7
The progression is as follows:
1Maj 2min 3min 4Maj 5Maj 6min 7dim
You never leave the C scale when playing any of these chords.
CMaj=C E G Dmin=D F A Emin=E G B FMaj=F A C GMaj=G B D Amin=A C E Bdim=B D F
At this time there is no need to go into a minor scale because these songs are played in a Major key, not a minor. They do at times use minor chords, but the notes used are all the same.
Understand the difference between a minor chord and a minor key.
A minor chord is 1 3b 5. Take the 3rd note in the major scale and move back 1/2 step (also called flatting it). So Cmin is C Eb G
For minor key, the scale is 1 2 3b 4 5 6b 7b . So the Cmin scale is C D Eb F G Ab Bb.
(You would also need to understand diminished if you are trying to approach a song with theory. dim = 1 3b 5b so Cdim = C Eb Gb)
These are just the basic rudiments of triad (or three note) chords. Unless you understood a whole lot more than this, taking a theoretical approach to learning a song is one big headache. You'll get there in time, but for now concentrate on getting the notes involved and put theory to it later.
