I want my partner of 7- 8 months to adopt my son but I do not want to ask permission from the father we ended our relationship before the birth of our son and he is now in prison and is not on the birth certificate can he stop the adoption

You need a signed consent from the father in order to proceed.

In many States you need to be in a stable relationship in order to adopt - and stable is defined as married for a year or longer.

Agreed, in many US states, you will have to be married, and in others you will have to be in a longer term relationship, ( often at least a year)

But in call cases you will have to notify the father and ask his permission