I received a 1099-NEC from previous employer. I also sold their stock I acquired. Do I report 1099-NEC

Probably not. Form 1099-NEC and Form 1099-B are two different forms. Form 1099-NEC is used to report non-employee compensation, i.e. money you earned performing services for your former employer.

It is usually unrelated to the stock your acquired and sold unless your compensation was somehow connected to your rights to acquire the stock. This is not common.

We’d have to know more about how you acquired the stock. It you bought the stock on your own (even if you used money you earned from the company) then is it unrelated.

If your 1099-NEC included some stock rights, then you made be able to include some 1099-NEC income as part of the cost, but again, we’d need more details.