Connecting a Rectangular Face with Curved Edges to a Circlular Face

I’m having trouble finding a forum/tutorial that’ll help me connect the curved rectangular surface and the circular one. Can anyone please help?

Ideally I’d like the four corners to connect to the edges of the sphere.

I’d use Curviloft to do that. You can get it from Sketchucation.

Screenshot - 4_27_2020 , 8_58_07 PM

FWIW, you’ll get the best results if the circle and the square with rounded corners have the same number of segments.