Migration Assistant: Files missing on MacBook Pro

frazerandmac wrote:

I used Migration assistant to move all my files and folders from old MacPro 2010 to new MacBook Pro 16” 2024. I see my desktop folder aliases but can’t find the original Folders and files. I did not create a new user on the laptop

you do not say what was the OSX or macOS— non the less That is a huge jump in machines...

You can try from Finder>Go>Go to Folder, copy & paste:

/Users/Shared/Relocated Items

... see if original items are there or not(?)

ref: About the read-only system volume in macOS Catalina or later - Apple Support

The old rule of thumb was limited to jump 2 operating systems only to avoid issues moving your user account...

You appear to have jumped 13-15 operating systems(?) depending — all bets are off.