Congratulations! I hope this is because you practice the faith and intend to raise your children Catholic.
I don’t know who told you this, or if you just assumed it, but it is not true. Your girlfriend does not need to be baptized in order for you to marry her in the Church. You should meet with your pastor. You need what is called a dispensation from disparity of cult. Your pastor applies for it with your bishop.
She should be baptized if she believes in God, wants to join the Church, and plans to be a practicing Catholic. Is she “convinced” to be baptized because she really believes or because she just wants to get married?
It is wrong to coerce someone to be baptized.
To be baptized, she would approach the priest and ask about instruction in the Catholic faith. After she takes instruction, however that is done in your country, then she would be baptized, confirmed, and receive first eucharist.
But again, she should seek baptism if she really believes, not just to please you. I hope she will be baptized, but not if it’s under pressure.