$F(x,y,z)=\Sigma_m(0,2,4,6) = x'y'z'+x'yz'+xy'z'+xyz'$
Complement of Function,
$F'(x,y,z)= (x+y+z)(x+y'+z)(x'+y+z)(x'+y'+z)$
$F'(x,y,z)= \Pi_M(0,2,4,6)$
$F'(x,y,z)=\Sigma_m(1,3,5,7)$
Dual of Function,
$F_d(x,y,z)=(x'+y'+z')(x'+y+z')(x+y'+z')(x+y+z')$
$F_d(x,y,z) = M_7.M_5.M_3.M_1$
$F_d(x,y,z) =\Pi_M(1,3,5,7)$
$F_d(x,y,z) =\Sigma_m(0,2,4,6)$
Note:
In Dual of $f$, that is $f_d$, we replace AND $(.)$ by OR $(+)$, OR $(+)$ by AND $(.)$, $0$ by $1$ and $1$ by $0$ ONLY.
In Complement of $f$, that is $f'$, we need to replace all variable, say $x$ , by it complement variables , say $x'$, also.
Refer : https://gateoverflow.in/36297/computing-the-dual-of-the-boolean-function