If you are being asked this, you might have been given sources that have the information you need. I do not have the numbers you need, but I can give you some suggestions on what to look for.
Economic migration has impacts on both the sending and receiving countries. When we are thinking about the impact on the sending country, the main economic impact comes through remittances. Workers who leave a country to work abroad often send money to relatives back home. These remittances can form a significant portion of a sending country’s GDP. This must be balanced against the negative consequences of such immigration. Such immigration may weaken a country socially because it takes so many people away from the country and lowers morale. It may also amount to a “brain drain” of sorts as the most ambitious workers move away from the country.
As for the receiving country, the major benefit tends to come in the form of cheap labor. Consumers in countries like the United States benefit greatly from the low-wage labor of economic migrants in areas like domestic service and restaurants. The negatives for such countries depend on whether the immigration is legal and on the extent to which immigrant groups call on the government for services.
Thus, in order to assess the impact of economic migrations, you should try to assess how much countries are affected by these things.