Help transplanting burr oak saplings

Last autumn I stored several acorns in a 5-inch pot that was filled with potting soil and covered. I took the cover off 2 days ago to discover 7 saplings between 3 and 7 inches long. They are too big for the pot I was storing them in. Are they safe to transplant at this stage? What size pot should I transplant them in? How do I...