Must I perform the Fajr prayer as a make-up before the Dhuhr prayer after performing ghusl from janabah?

You have committed a great sin by missing the Fajr prayer until its time expired, for abandoning prayer is one of the gravest sins by the consensus of Muslims. You must offer sincere repentance and remorse for this sin, then make up this prayer according to the majority of scholars, with the obligation of maintaining the order between the two prayers; so you perform the missed prayer first, then the current one, according to the majority.