Hi @Annalisa_Ferri - there isn’t a built-in way to do this as bases cannot be directly connected or share common data. Using the API, you could come up with a syncing process - either one-way or both-ways. Needs a bit of coding expertise to make this happen however.
The manual way to do this is to download the data from the table in base A and import into base B (assuming the tables are the same structure in both), but, obviously, this isn’t an automated process so someone would need to do it every time you want the data synced.
To import, you can create a new table by importing a file (csv or other formats), but this is more of a one-time deal. If you want to import regularly, you can use the CSV Import Block (although you need to be on a paid pro plan for access to this)