This cannot be done in a single microflow. Since a microflow will execute client actions at the end of the microflow.
However this can be solved in 2 ways
Can be done in a microflow using the session and a call to itself. During first run, check the session, if no confirmation value is found, continue upto the point of confirmation, and show the confirmation page. Confirmation page having a yes and a no button. Yes sets the session and calls the same microflow. But I advise against that since it is ugly programming.
Just adding my bit if you're doing native development, then you can actually call on a confirmation activity within the action nanoflow. Here is an example.
I haven't tried this in a web client, but it should hypothetically work as well.
Best regads,
Wouter