My 6 month old puppy wan't eating or drinking, he vommited and also had dirrerhea. We took him to the vet and he tested postitve for parvo. They admitted him and said the medicine they give him is a strong dose. We admitted him last night and when we went to see him today he didn't look better nor worse.. I'm just wondering if anyone has experienced this and how long I should give him to be in there and actually believe he will recover.. I've talked to three different doctor there, twy've all said something different. Two said they don't think he is doing good but the one who admitted him says he believes he will recover. I hear if they are in there for 3 days they will recover.. Its been a little over 24 hours and he still won't eat or drink..

My puppy had parvo and was in the hospital for a week. It then took her about 3 months to recover fully. Remember that parvo is a virus, it has to run its course.

I'm not a dog expert. I am only speaking from personal experience. Hopefully one of our pet experts will come on and give you more in depth advice.

Unfortunately, there are no guarantees, Parvo is very unpredictable.
I'm also not sure what you are referring to by "medicine". Antibiotics, anti-nausea meds, and IV fluids are pretty much the standard for treatment. Each case if different, but the supportive care is key.
There is no 3 day rule, a pup can have a good morning and turn around and have a bad afternoon, and vice versa,
I hope your pup does well, and rest assured that hospitalization is the best option for a chance of recovery.
The parvo survivor that lives at my house was hospitalized for 6 days, and on fluids for 5 of those days, and more than once we thought we would lose him. It is at best a day to day illness/recovery situation.