Upgraded my world to new 26.1 but it loads an old ver instead of the latest ver

(1) Today when I upgraded (from 1.21.11) my survival world into the newest version, 26.1, it basically showed me a version before I added some obvious features to my base (exp farm + lower floor of my base + destroyed kelp farm, etc)

Now, I have a back up of this world on a thumb drive, when I loaded that back up (in 1.21.11) it showed me that I did have those items, the exp farm + lower floor of my base + no kelp farm

When I tried to load this back up again in 26.1, it reverted back to (1)