I have a lot of qadha prayers to make up, over 3000, because I did not used to pray when I was younger. I pray one qadha prayer per day and find it difficult to do more than that. I think I become discouraged from the amount of qadha that I have. Do you have any advice as to how to motivate myself to insha'Allah do at least 5 qadha prayers per day instead of just one?

You can do only the wajib parts of the prayer.
This will shrink the prayer time, and you will be able to make qadha of a day in about 10 minutes, which is very short time.