To find the impulse you multiply the mass by the change in velocity (impulse=mass×Δvelocity). So in this case, 3 kg × 12 m/s ("12" because the object went from zero m/s to 12 m/s).
The answer is 36 kg m/s
It makes no sense how you typed this problem out.
I believe the website www.asanet.org will help (:
Given: Velocity of light c = 3.00 x 10⁸ m/s
Frequency f = 7.65 x 10⁷/s
Required: Wavelength λ = ?
Formula: λ = c/f
λ = 3.00 x 10⁸ m/s/7.65 x 10⁷/s
λ = 3.92 m