Search these locations:
For Desktop folder:
Open File Explorer > This PC > Desktop
Find your old data:
C:\Users[YourOldUsername]\Documents
C:\Users[YourOldUsername]\Downloads
C:\Users[YourOldUsername]\Pictures
You have to reinstall Outlook, Office.
Where have you seen the "select a child tag" message?
As Best Buy did the data transfer from your old PC to the new PC it will be better to contact Best Buy’s Geek Squad and ask them on this issue.