in the project settings under the “saving and loading” section on the left make sure “save content” is checked, then it should save your content as “uasset” then you will just have to go into the file explorer and copy or move the files into your current projects content folder (where ever you want them as long as theyre in the content folder) and theyll appear in your content browser im sorry, as far as you uassets not showing up im afradi thats because you might not have had that option set as true and as far as i know im pretty sure they may be lost.