It’s quite difficult from your description to tell what’s going on. Can you better describe it?
You write: “I can see them on project” and “I still can’t import old arduino project”. So does it work or doesn’t it? Or do these sentences refer to two different projects?
Where is the project located that doesn’t work? Have you checked with the Windows Explorer that it’s there?
“I can see them on project”: What does that mean? Where can you see it? In a folder in the Windows Explorer? Or in Visual Studio Code? If so, in which view?
Also note that due to PlatformIO’s funny integration, security tools (such as local firewalls and virus scanners) can interfer with PlatformIO and in particular with the PlatformIO’s unfortunate file selection dialog. Check if it makes a difference if you turn the security tools off.