Is My Platy Pregnant

I don't know if my red top platy is pregnant and how far she is any ideas ?

I can see lots of black dots I her belly

If there are males and females in the tank (or were at any point in the past ~6 months) the answer is yes.
 
http/www.fishforums.net/index.php?/topic/417438-how-to-tell-if-your-guppymollyplaty-or-swordtail-is-pregnant/

I would say she has at least ten days, maybe even longer, to go yet. 

When should I put her in the breaders trap

When the corners of her belly go square, and she starts hiding at the bottom. Be warned that if you put her in too early, it can stress her fatally.
 
Also bear in mind that she will have an average of 30 fry every 4-6 weeks from now until 6 months after her last contact with a male. If you currently have a male in the tank, that means she will keep having fry drops until 6 months after he dies. Do you have the facilities to care for that amount of fry. Alternatively, do you have a reliable outlet for them, someone who will definitely take that many fish. Not many LFS will do that, they can get them so cheap from their trusted suppliers, why would they risk the health of their systems from an unknown home breeder.
 
In the wild, the majority of fry will be eaten, that's why they have so many in a drop. In your home aquarium, if you have a good level of cover, some will survive, but others will be eaten, and this naturally controls the numbers of fry that you have to find homes for.
 
Just some food for thought, as it were.