Smooth a curved part?

[achqes]

Does anyone know a plugin or something that could help me make this union smooth so that none of these lines show?

[Crazedbrick1]

Try changing the SmoothingAngle.

Any number between 30 and 70 degrees should work fine.

[C0WlNG (Bruce)]

The way I do it is I first <Right click on the object <Shade smooth the go to the <Object data properties <Normals <Auto smooth

[grimmerschool2 (FestiveGrim)]

He clearly meant a union, not a mesh.