What do I do if I missed joined prayers?

So basically, I have a list of prayers that I missed over the years due to multiple things (not laziness), and have finally got around to making them up. Two of the prayers are the Dhuhr and Asr which I planned to pray together, but happened to miss. Do I have to make them up together? Or can I do so individually? Please give me a very clear and direct answer to this.