C9 guitar chord is also written as C9 or Cdom9.
Guitar chords chart for C9 chord with suggested finger positions on the guitar fretboard is shown below.
View 9 chord for guitar with other root notes
C - D - E - F - G - A - B - C♯ - D♯ - F♯ - G♯ - A♯ - D♭ - E♭ - G♭ - A♭ - B♭