Which string is the primary basis for the D chord

When you play the D Minor Chord you can do as follows ...

Keep your 3rd finger on the B string, from your previous placement when playing the D major chord

Then take your 1st finger and place it down onto the 1st fret of the high E string

Finally place your middle finger on the G string 2nd fret

And like before you want to make sure that you are playing that D root note.