I have owned two houses where I have had greenhouses built off the back but neither was a conversion. The last one was the most efficient. It had a foundation with a knee wall but no solid floor and I had ferns and begonias growing under the benches. There were cedar steps and planking in the middle that we used to access the plants. One thing that I regret not doing was adding a ceiling vent. There were two side windows and a door but still, way too much heat would build up in it, even though we used shade cloth during the summer months. Hope this helps. lisa

my husband got some at a home depot or Lowes or feed store that were not as wide. He used a grinder and cut them down. Used them to make squares to put heavy tomatoes in. Used hog rings to hook together. Now I am wondering if you could find some of the plastic covered wire closet shelves and use them. I used a bunch (got inexpensive at ReStore Habitat for Humanity) I put them up and down vertical on fence to keep basketball out of the next yard. Then I bought more and cut with a hack saw and put together to make a gazebo or garden room of them. I will be using them to grow vines up. That might be a good thing for you to look for. I just used tie wire like cement men use on the rods to tie together.

He has some nice pics. Maybe contact him. https://www.houzz.com/pro/doug-lockwood/dig-doug-s-designs

Have no idea how large your footing is or it's shape, so how much to move the structure over is unknown. The posts should land on the footing, and if the same anchors are reused, refer to the manufacturer instructions on how close those bolts should be to the edge of the footing. Absent that use minimum 2 1/2" from edge for 1/2"dia bolts. That will determine where posts are placed and the pavers will enclose around that. Don't install the structure based on existing bolt holes in pavers, install it based on your footings. Deal with aesthetics of unused holes as you wish. The structure's connection to the footings, to generally describe it, help prevent the structure from folding over on itself.