Scales to Play Over Cm6
Every chord is a subset of several scales: any scale that contains all of a chord's tones fits over it. Pick a chord to see the matching scales from its own root, the major keys the chord belongs to, and full fretboard diagrams for every scale on guitar.
A Cm6 chord contains the notes C – D# – G – A. Any scale that includes every one of those 4 tones fits over it — from the root C, that means C Melodic Minor, C Rock 'n' Roll, C Dorian, C Dorian Bebop, C Half Whole Diminished and C Gypsy Major. Start with the first scale listed: it is the most common choice, and the others color the same chord tones differently.
Cm6 is also diatonic to one major key: A# major (relative minor Gm). In a song from one of those keys you can also solo with the key's own major scale or its relative minor pentatonic across the whole progression, not just this chord.