Migration assistant has been at "preparing to transfer user documents" for 4 hours to new MacBook Air from 2012 MacBook Pro, that seems too long. Any suggestions

Wireless transfer often just doesn't work. Make a Time Machine backup of your old Mac and migrate from that Move your content to a new Mac - Apple Support

I'm about to buy a new MacBook Air as my 2009 MacBook died, so I'll be doing the migration soon (I'm a tech idiot). thanks SeaPapp for this advice and for providing the link to how to do it!

You’re welcome. If you have any questions after you het your new Mac just post them in a new thread. Great group of people who are willing to help.