While the stamp packs were written for Gaia 1.x, they may still be used with the newer versions of Gaia by simply running the stamp folders through Gaia’s stamp converter tool located in the Advanced tab within the Gaia Tools foldout. Once you have done this, the stamps should work with Gaia 2.x and Gaia Pro with no problem.
Unfortunately there is not a conversion for sessions, or at least there wasn’t going to be one the last time I spoke with Adam. I haven’t had a chance to check out the latest updates to see what has been added. So to my knowledge if you want to run the sessions, you would still need to do that using Gaia 1.x on an older Unity install. To be totally honest, with all of the new features/tools available, I’m not sure why anyone would want to use them as the terrains you can create using the stamps with the new Gaia tools should be far superior than the original sessions made with Gaia 1.x.
Gaia 1.x stamps may be used with Gaia 2.x by using Gaia’s built-in Stamp Converter Tool
As always, if you run into issues you may feel free to contact me via private message here on our Facebook page or at our support email address located on the stamp pack’s page on the asset store.