What is the dialing code for Ardara Co. Donegal Ireland?

Most of County Donegal is in area code 074, but the southern bit, including Ballyshannon, is in area code 071. In international format, that's +353 74 or +353 71.

(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.)