Recover data after formatting the Maxtor external HDD

My external HDD which bought from Maxtor was formatted by mistake the other day. Consequently, all files and folders saved on it have been lost now. Those files contain pictures, word documents, clients information, and so on. What I want to express is that those contents are very important for me ands I can not afford to lose them at all. Anyone could kindly help me get them back?  -Susan