How much time will it take me to learn 3d game programming ?

Hi, I can program 2d games with ease in java and html5, but I now wanna get my hands on making 3d games but it looks scary. According to you, how much time will it take an average guy with just knowledge of programming and high school mathematics to learn 3d game programming?
p.s. - >I don’t know anything about 3d.
>All translations, rotations, scaling etc I have ever done is in 2d (canvas), which is very easy.
> I don’t know what mathematics I need to make a 3d game.
I am a self-learner. In which direction should I go and what should be my first step ?