You'll have to wait....and wait...for a long time At that size, they're little more than a cutting and will need a couple of years or so of potting on, before planting out and getting to a reasonable size. You'll need to pot them on this year with a decent, soil based medium and then just make sure they don't get dried out. They'll just grow at their own pace. Once they're filling a bigger pot, you can plant them out.
Silver surfer said:
They are bushy multi stemmed shrubs that will soon be covered in tiny pale pink flowers.Then the leaves will grow.Leaves will go deep red in the autumn.They do grow fairly large and very bushy so make sure you give them plenty of space.Once ground warms up plant asap.
All types of flowering cherry are dwarves compared to this one https://www.boredpanda.com/japans-oldest-cherry-tree/