Hi Wendy,
If you have CC3 pipeline ( which I strongly reccommend)
you could actually keep your older 6.5 for creating/saving imotion
files and attach any Imotion or imotion+ file to any CC3 Avatar during the export process from CC3.
There are export presets in CC3 for the major 3DCC apps & engines like MAya C4D Blender
unity UE4,
I used the Blender preset for the animation I posed up thread
I cannot offer any advice on going from CC3 to Carrarra.
You wont be able to use any of the CC3 avatars in version 6.5 but you can save them locally
as converted CC3 content in your CC3 libraies including clothing ,shapes skins and hairs from genesis 1,2,4,8.
or even imported custom clothing meshes as I do since I develop my own.
The CC3 cloth rigging tools are far better than the Daz tools
Like you,I still have version 6.5 pipeline installed on my older PC
but I did upgrade to the base version of 7.x on my new tower
During the 50 percent off 'Covid 19 " sale that ended last month
This allows me to use my converted Daz people directly in iclone and use the Digtal human shaders
clothing and hairs and improved animation
tools in version 7.x.