How to set floor height even on multiple parts in a part file?

I'm fairly new to Solidworks and Photoview 360. I am trying to set the floor height even for 3 objects in my part file (see attached image below).

I want them to stand on the floor at even height since the image right now is unrealistic.

I have been struggling to work it out but no result.

Can anyone advise on this please? thanks advance!

SolidworksGeneral