sort file name based date

in dir c:\mydir\ have a variuos .txt file(only this format)

the single file name have this structure:

aaa0_01-05-2013
aaa1_02-05-2013
aaa1_02-06-2013
aaa1_01-05-2013
aaa2_01-05-2013

i need to store the file name in to an array and loop it based aaa(x) and date

how to?