First, I would be very cautious. Several of these cribs were recalled. You can check the Consumer Products Safety Commission to see if your crib was involved.
Secondly, this company went out of business and I was unable to contact anyone about ordering parts or manuals.
If you have the manul, it will tell you how many and what size screws you need.
If you don't have that I would try measuring the distance the screws need to go this will tell you the lengh of the screws needed. Then measure the distance of the hole, this will tell you how large of a screw to buy 1/2" 1/4" etc.
You can take this to your local hardware store such as Ace, Home Depot, Lowe's and ask them to help you pick out the correct items.