Please try this
System.Text.RegularExpressions.Regex.Matches(str,"(?<=\d\)).*")
This should be given in assign
Output type is matchcollection(create a variable of this type and use the variable on left side of assign)
Use a for loop with in as matchcollection variable and type argument(you will find in properties panel of for loop) as match and inside the for loop you will get the result as currentitem.value
This will give all 3 file names
Cheers