This is my query:
set dateformat mdy;
select cast([File Date] as date) as 'test' from gpdetail
Msg 241, Level 16, State 1, Line 2
Conversion failed when converting date and/or time from character string.
The place to start is with the
select [File Date] from gpdetail where isdate([File Date]) = 0;
This may find places where the date does not conform.
If you just want to ignore badly formatted strings, then try:
select (case when isdate([File Date]) = 1 then cast([File Date] as date) end) as test from gpdetail