Pediatric and neonatal NPs are not interchangeable. The education is entirely different. It can be v. challenging for new grads to find jobs in specialty areas. However, some organizations/facilities are willing to hire new grads into specialty units. You can improve your chances by being willing to relocate in order to get a job in a specialty you really want (the more of the US you're willing to consider, the better your chances).
Even if you aren't able to find an NICU job right away and have to spend a few years "working up" to that, in the long run, over your entire career, that will be just a tiny "blip on the radar" (although I realize it seems like a huge deal now
). Plus, many of us think that it is a v. good idea to have at least a few years of clinical experience before pursuing grad school.
However, keep in mind that many, many
students (including me, back in the day) have had the experience of starting nursing school
quite sure that they know exactly what specialty area they definitely want to pursue, only to find that, by the time they finish school or early in their careers, they are much more interested in something entirely different. Nursing is a v. "big tent," and there are lots of career paths and roles that people aren't even aware
of until they've been in the nursing world for a while. I encourage you strongly to keep an open mind as you go through school.
Best wishes for your journey!