How to create dome in solidworks?

Here's how I'm seeing the geometry, pics attached.

I see a loft, a revolved cylinder, and a cut. I have a newer version of solidworks than you so you'll only be able to open the step file, hopefully the pictures guide you well enough.

Also, regarding 'Boss-Extrude1', I would recommend not using "half dimensions", ever, if the intent is symmetry. It will come back to haunt you unless you write an equation to control it, and really, who wants to write unnecessary equations.

Best practice is to use relations to control design intent. Strive for as few driving dimensions as possible in a sketch.

In the 'do this instead' picture, centerlines were added to apply "symmetry" across the origin to the sketched square, and since the intent is the shape is to be square, "equal" relation was added to a horizontal and vertical line, reducing the dimensions required to fully constrain the sketch to a single dimension.

Good luck with your model!

There having direct command for dome go to Insert-features-Dome

Hi,
I would suggest instead of lofting from square to circle, just extrude a square, then do a 'lofted cut' on the corner to achieve the shape which you want.

It seems to be a simple extrusion of a square, then a revolved cut of a triangle as in the attached image...
The dome can be added either by "Dome" feature, or a simple revolve.