You could use Join or maybe even Concatenate to merge surfaces together. But it seems like an odd thing to do based on the attached image - the edges show all the fillets (and sharp corners). And the model is solid geometry, not surfaces. It looks pretty smooth to me.
I suggest just changing the Render Style to something without edges, such as Shading (SHD) so you don't see all the patchwork. Shading With Material will also make it look better.