What form to use for sale of shares in a private company after they vested. Not reflected in wages and no 1099B form. Thank you.

Greetings, I have a situation where I was granted shares in a private company and needed to buy in for those shares for which I have a cost basis.  This company was then sold to another private company and my shares vested and I received proceeds after about five years.  What form would I enter this transaction under?  There will be no 1099B type from coming from this transaction nor is it reflected in my wages.  I just received a check.  Thank you.