What I found out is that Electrolux bought Poulan some time ago and they were the ones responsible for changes to a number of products, including the weed trimmers. Apparently they couldn't make up their minds on the carbs because, as I understand it, there are a number of versions that were used until recently.
Anyway, the black center parts in the photo are the adjustment screws. Since I bought a replacement carb, I have decided to remove the screws from the old one, slot them and then replace the ones in the new carb with ones I can adjust.
I had taken the weed trimmer to Northern Tool which is an authorized repair place and had the mechanic look at the trimmer. After I explained what it was doing and what I did, replaced the carb, he was able to get it running right by making some carb adjustments. Now it starts and runs as it should. So, if I remove the current screws and keep track of the number of turns, I should be able to put my (now slotted) screws in at the same settings and have a running trimmer again.
Thanks to all of you that contributed to this Thread and provided helpful input towards resolving this issue. I hope that the info shared here will be of help to others as well.