You can find errored rows if you use ssis by adding OnError action to redirect row. Otherwise you might have to do it it two steps first get file data onto staging table, then do required validations to find offending rows and insert the correct ones.
BTW I dont want to do major changes. if there is data issue the whole file should not upload like the current process.
just want to know which row errored out.
Is there any good link for ssis and Onerror which you have mentioned.
Still if you want row wise tracking of errors you obviously need a row by row parsing mechanism. That can only be possible using SSIS file source or using staging table approach
Alternatively you could use a language like .NET to create a file system object and load and parse the file but again that can cause performance issues especially for large files. My preferred method is using Staging table approach if in T-sql or using SSIS otherwise.