Gazebo model (stl, dae) not spawning on ground plane, floating [closed]

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Hi! I'm working on building my own gazebo environment and I have a problem when the models (dae, stl) I open in gazebo 'floating' above the ground plane when the models weren't made on the XY plane in the CAD software.

Is there a way to make the bottom face of the object automatically spawn on the ground? I've gone into the .world file and can edit it to have the pose offset but that requires me to know what that exact offset is.

Thanks!