Report to estimate workload in all backlogs

[Aquive]

I'd like to have more insight in how much story points of work all the backlogs combined have remaining. How would I achieve that. I have some ideas, but I am new to Jira and especially its reports. Not all the stories have story points assigned yet. We assign story points as the issues get closer to be planned.

So my idea would be:

1. Get the number of completed stories
2. Get total amount of story points for these stories
3. Calculate average story points for each story
4. Get stories from backlog without story points
5. Calculate the prediction for these stories (stories count * average story point calculated at step 3) 
6. Get all stories from backlog with story points
7. Add the prediction and the real story points from step 6 together
8. The result is the predicted workload as story points
9. The best would be to plot this on a daily or weekly basis on a graph to see trends

Is there an existing report which does this? Or something similar. If not can I make such a report in Jira? The best would be to do this on all boards combined.

Thanks in advance for any help!