I am part of the WIC program.I want be able to get more formula until next week.I have a little bit of formula left.can I mix the formula i have left with regular milk?and if so what kind of milk would be the best?i'm just trying to stretch the milk until i can get the formula

I wouldn't do that, the baby for one could have an allergic reaction to the milk. You should not give them cows milk at all until they are about one years old. I know how it is I have twins and am a single mom and am on WIC, sometimes I run out and have to ask everyone to borrow me money just so I can buy formula for them.

When you do start to make the switch, and as mommyoftwins mentioned, baby should be a year old before you do, some people do mix a bit to have a gradual transition. When you do go to regular milk, stick with whole milk. The extra fats are important for your baby's development over the next couple of years. If you can still get the formula... even better to be on that awhile longer even after a year old, especially if they aren't eating a varied diet of solids just yet.
Nothing magic happens once they hit a year old, it is just that is it known that most babies by that age will have mature enough digestive systems to handle the regular milk better. Some will probably do OK sooner, some would benefit from waiting longer. You just don't know which side of the fence your baby may fall... hence the recommendation.