How do I view my Son's(dependent) social security number? I need it for enrollment in school and can't find original?

If you filed a tax return with him as a dependent his SS number will be on the tax return.

To access your prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/

Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show.  Click on the Year and Click on Download/print return (PDF)

If you used the desktop CD/Download editions installed on your computer, the only copy of your tax data file and any PDF's will be on the computer where the return was created.  TurboTax does not store online any returns completed using the desktop editions.

Or you can go to the Social Security website and request a copy of the SS card for him - https://faq.ssa.gov/en-us/Topic/article/KA-02723