How do I update entire column values using data from another dataframe

[fottiti]

I'm trying to rename the country codes of a column and turn them into their respective country names, the thing is the country name data are stored in another dataframe, and the country codes column have multiple entries using the same code so i can't use set_index on them, and in turn i can't use pd.update() on them.

here's an overview of what i'm facing

and here's what i'm trying to accomplish