Try this trick to get the one-to-one connection between numbers and objects.
Put some beans on a table. Shuffle them about, removing a few of them. Ask your child how many beans there are. Shuffle them again, removing or adding beans, and ask again. With each round, ask your child to count each bean separately, touching each one as he counts aloud. In this way, he will see the one-to-one connection between number and object.