The dimensions of couple are
$M{L^2}{T^{ - 2}}$
$ML{T^{ - 2}}$
$M{L^{ - 1}}{T^{ - 3}}$
$M{L^{ - 2}}{T^{ - 2}}$
The dimensions of couple are
Couple = Force $ \times $ Arm length = $[ML{T^{ - 2}}]\,[L]\, = \,[M{L^2}{T^{ - 2}}]$