If you were updating from a pretty old version of VSCode (>2 years ago) it’s expected to lose your saved connections. Apologies for this. We removed the migration from the old connection saving format a while back. VSCode also updated their internal credential storage system.
Getting the older connections now could be tricky and as a result of the VSCode changes I’m not sure it’ll be easy. You can check the Windows Credential Manager to see if there are saved connections from the VSCode extension. It’ll be a manual process of getting them out of there and into the extension again.
Related, something you may want to do is upvote this item on the feedback forum: predefined connections array on settings, this helps on devcontainer setups alot – MongoDB Feedback Engine
That’ll make it so we prioritize a more transparent way to save connections for folks. It should make things like exporting and backing up easier so this never happens again down the line.