Linda, when they are young, size correlates directly to how much and how regularly they eat. Based on those photos (and comparing to personal observation of head-started hatchlings here)I would guess that that turtle could be anywhere from 3 to 12 months

Try not to worry too much about it not eating at the moment: they are well equipped to go for long periods without food.
Tasty treats to offer are wax worms and, if you can find them, small slugs.