"Filtering->Vapoursynth->DeNoise->mClean" it's there you just have to scroll down, should be the 11th filter in the DeNoise-tab (unless I miscounted).
or "Filtering->Avisynth->DeNoise->Denoiser->mClean" (last in the drop-down)
or "Filtering->Avisynth->DeNoise->Denoiser->mClean" (last in the drop-down)