There is no area code +1 381 in North America (USA, Canada, etc.).
Country code +381 is Serbia.
(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, and many other countries use different prefixes.)
The country code and area code of Bor, Serbia is 381, (0)30.
The country code and area code of Laximpur, Bangladesh is 880, (0)381.
The country code and area code of Rostock, Germany is 49, (0)381.
The country code and area code of Beograd, Serbia is 381, (0)11.
The country code and area code of Cacak, Serbia is 381, (0)32.
The country code and area code of Dakovica, Serbia is 381, (0)390.
The country code and area code of Jagodina, Serbia is 381, (0)35.
The country code and area code of Kikinda, Serbia is 381, (0)230.
The country code and area code of Kragujevac, Serbia is 381, (0)34.
The country code and area code of Krajevo, Serbia is 381, (0)36.
The country code and area code of Krusevac, Serbia is 381, (0)37.
The country code and area code of Leskovac, Serbia is 381, (0)16.