#### Answer

$3m(m+3)(m+1)$

#### Work Step by Step

Factor out $3m$ to have:
$=3m(m^2+4m+3)$
The leading coefficient of the trinomial factor is 1.
To factor the trinomial, just look for the factors of the constant term (3) whose sum is equal to the coefficient of the middle term (4).
These factors are $3$ and $1$.
Thus, the completely factored form of the given expression is:
$=3m(m+3)(m+1)$