Try to find their mom!  No one can better take care of kittens than their mom! If you are certain they are orphaned,  Sue Freeman has a great web site with information on how to care for for orphans and how to determine the age of kittens: http://www.rescueguide.com/orphkits.html

We have not had good results with KMR brand of kitten formula, which she recommends.   We have done better with Pro Bio-Lac or powdered goats milk which you can buy in the nutrition section of Fred Meyers where the baby food is. 
You can also syringe feed Pedialyte (unflavored) to help re-hydrate kittens, which the web site does not mention.