Rhino paste with units between files

i am trying to paste an object from one 3dm file to another, both with different units.
I remember that rhino use to pop up a prompt saying that the object is copied from a file with different units, and do you want to change the scale. But somehow it dosent anymore.
now it just pastes and shows up with the wrong units
I wonder if i can get that prompt back.
or paste with units

Not exactly all that helpful but I tried that just now - one file with feet as units and the other with mm.
Drew a cube 10x10x10 in the first and copied over into the second.
I don’t get a message warning about different units and when I measure one of the edges in the second file, I get 3048 mm.

Hi Timo - is the desired result that the pasted object would have the same number of units, so to speak, in the new units as it had in the originating file? i.e. Wim’s 10 foot cube would paste as a 10 mm cube in the mm file?