LATAM key means you could activate this code in Antigua and Barbuda, Argentina, Barbados, Bermuda, Bolivia, Brazil, Bahamas, Belize, Chile, Colombia, Costa Rica, Cuba, Dominica, Dominican Republic, Ecuador, Falkland Islands (Malvinas), Grenada, French Guiana, South Georgia and the South Sandwich Islands, Guatemala, Guyana, Honduras, Haiti, Jamaica, Saint Kitts and Nevis, Saint Lucia, Mexico, Nicaragua, Panama, Peru, Puerto Rico, Paraguay, Suriname, El Salvador, Uruguay, Saint Vincent and the Grenadines, Venezuela.
I suggest that you can register a new steam account ( Argentina is the best, because most of games are very cheap). You can google how to register a Argentina steam account. (Whether you can activate the key depends on your steam wallet area. But I don't recommend that you change the wallet area of your existing steam account because it violates the steam rules.)