All you really need to know is that to be Protestant and profess a belief in Sola Scriptura is to embrace cognitive dissonance. To accept the the Canon of Scripture they must accept the authority of the Church while professing to disregard its teachings. No wonder they are so confused.
Our old Testament follows the cannonicity of Judaism, while the cannon of the New Testament was universally accepted well before the events giving rise to the Reformantion.
“One cannot have God as his Father, who does not have the Holy Catholic Church as his Mother!”
St. Cyprian of Carthage