How can I add a column based on matches on two other columns?

Question

I am looking to create a dataframe "df3" based on two other dataframes: "df1" and "df2".

Say I have these dataframes:

Dataframes 1&2

I want to add the population from df2 onto df1 based on the ID and Year columns. Such that I have df3 which looks like this:

DF3

EDIT:

I have tried df3 = df1.merge(df2, on=['ID', 'Year'])

but this results in this error:

>
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-29-882d6f907355> in <module>
----> 1 aps_all_pop = aps_all.merge(pop, on=['ID', 'Year'])
      2 # Add Population
      3 
      4 # Run a loop to find per 1000 figures

/opt/anaconda/envs/Python3/lib/python3.8/site-packages/pandas/core/frame.py in merge(self, right, how, on, left_on, right_on, left_index, right_index, sort, suffixes, copy, indicator, validate)
   8193         from pandas.core.reshape.merge import merge
   8194 
-> 8195         return merge(
   8196             self,
   8197             right,

/opt/anaconda/envs/Python3/lib/python3.8/site-packages/pandas/core/reshape/merge.py in merge(left, right, how, on, left_on, right_on, left_index, right_index, sort, suffixes, copy, indicator, validate)
     72     validate=None,
     73 ) -> "DataFrame":
---> 74     op = _MergeOperation(
     75         left,
     76         right,

/opt/anaconda/envs/Python3/lib/python3.8/site-packages/pandas/core/reshape/merge.py in __init__(self, left, right, how, on, left_on, right_on, axis, left_index, right_index, sort, suffixes, copy, indicator, validate)
    666             self.right_join_keys,
    667             self.join_names,
--> 668         ) = self._get_merge_keys()
    669 
    670         # validate the merge keys dtypes. We may need to coerce

/opt/anaconda/envs/Python3/lib/python3.8/site-packages/pandas/core/reshape/merge.py in _get_merge_keys(self)
   1044                         right_keys.append(rk)
   1045                     if lk is not None:
-> 1046                         left_keys.append(left._get_label_or_level_values(lk))
   1047                         join_names.append(lk)
   1048                     else:

/opt/anaconda/envs/Python3/lib/python3.8/site-packages/pandas/core/generic.py in _get_label_or_level_values(self, key, axis)
   1682             values = self.axes[axis].get_level_values(key)._values
   1683         else:
-> 1684             raise KeyError(key)
   1685 
   1686         # Check for duplicates

KeyError: 'Year'

I would really appreciate any help!

Thanks