We're so glad you asked!
The US Bureau of Labor Statistics suggests that in 2016, there were 12.3 million 501c3 jobs in the US. To see these broken down further and by State, check out the article here:
Please note that this number does not include federal, state and local government or agency jobs, which are also PSLF-qualified. Recent BLS data suggests there are roughly 22 million Americans employed by government, bringing the number of total PSLF-qualified jobs in the US to over 34 million!