You can click Songs in the sidebar to display your songs in a list view with a number of column headings.
Right-click on the column headings to enable new columns, such as Date Added.
Click on a column heading to sort on that column.
Click on the small triangle in the column heading to reverse the order of the sort.
Click on a track to select it, e.g. the first or last of the newly converted MP3 versions of your purchases.
Shift-click on another track to select a range, e.g. the last or first of the newly converted MP3s.
Now right-click on this selection and use Add to Playlist > New Playlist (or prepare a new empty playlist first and drag to it).
Make sure the list is in the right order, Album column sorted as Album by Artist is usually best.
As before right-click on the playlist name in the sidebar and use Copy to Play Order to make sure this will be the order used.
Right-click on the playlist name and click Burn Playlist.
Select MP3 CD and click Burn.
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