which plane should I use?

3

Good morning everyone!

I sketched on the front plane.

Now I have no idea how I am able to put the hole on the top of that??

I am still confused about the advantage of Convert Entities?

And I do not know what's wrong with the third image. What is the usefulness of creating a plane in Insert/Reference Geometry?

Every feedback is much appreciated!

SolidworksParts And Features