You can migrate specs and catalogs from earlier versions to AutoCAD Plant 3D toolset.
Catalog files from earlier versions must be migrated to the current version before they can be used. For example, if you have catalogs in C:\AutoCAD Plant 3D 2021 Content that you want to use in AutoCAD Plant 3D toolset you can migrate them.
If you do not migrate catalogs that have been customized, you cannot update specs and may be unable to place components into the model.
For detailed information on migrating project specs and custom catalog content see Migrating AutoCAD Plant 3D Projects, Specs and Catalogs.