You already have abs.

The question is rather how long it takes to lose the fat that covers them. And it will be different depending on the individual, their lifestyle, their initial fat level, their motivation, their physical activity, their diet...

But it's probably faster than most people imagine, if you do it right. Animal proteins are to be preferred, to transform them into muscles through intensive work!

The question is badly asked…. you can have the best abs in the world, you won't see anything if they're hidden by a fat sheet… I think 6 months is a reasonable time, provided you do a lot of cardio and have a healthy diet. The lower the fat level, the more the abs are visible.

Then there's genetics... Some have 4 abs, others 8, most people 6…. But do not forget that the abdominals are built above all on the plate, and try to run 3 times a week.

 It depends on the starting point. If you're lean and have almost no fat, you could easily get fat after 3–4 months of training. On the other hand, if you are an obese person who has a lot of fat, particularly in the abdominal region, it seems to me that with a rigid diet (for example drinking enough water, eating fruits, vegetables and animal protein) , fasting without falling into anorexia, doing sports very regularly (4 times a week) in an intense way, we could have very good results between 8 to 12 months.

In my opinion, the best way to fast is to train, step by step, in order to be able to eat in a period of 8 hours (say between 11 am and 7 pm) two good meals well served, nutritious and drink only water (without abusing it) and tea during the other 16 hours.

Honestly, it depends from person to person. If you're someone who has been working out or keeping up consistently with your gym routine, it wouldn't take as much time for you to get your dream body as it would for someone who has barely ever worked out or given it a thought priorly.  

Having said that, an average man (who isn't overweight) would require about 15 to 21 months to get in the right shape. Whereas, for a woman, it could take up to about 26 months at most and 21 months at least. 

Nonetheless, this isn't applicable to everyone, if you are consistent in your efforts, you can get abs far quickly.