How to use aggregation on unique visitors

Matomo has a unique visitors on single URL.However, I want to create a custom report with multiple URL to be a group then get the unique visitors. What’s correct approach I should take, thank you.

For example.
Matomo has :
page_a.html has 100 page visitors and 2 unique visitors(Public User A & B).
page_b.html has 100 page visitors and 2 unique visitors(Public User B & C).

I want a report to group page_a & page_b becomes
page_x.html has 200 page visitors and 3 unique visitors(Public User A,B & C).