This is a simple linear bearing adapter.
After printing, all you have to do is pushing your LM10UU towards inside of the adapter then you are ready to go with a LM10UU - > 2020 Adapter.
If you are struggling with assembly, submerging part into hot water may help.
Other option is scaling model by 101%. But don't forget that it may be slightly loose.
( Massive shout to kerembyl - I "Remixed" all this from his thing. )