How to get the file name(s) from a Multi File Reader

I have a Multi File Reader reading a series of S3 files using a wildcard, and writing the data to Snowflake. There is a Mapper in between. Functionally, everything is working as expected.
I’d like to get the name of the file in which the data was read, and write it to a Meta_FileName column. How do I retrieve the file name from the Multi File Reader? I’m sort of assuming it’s an expression to be added in the Mapper but not sure. TIA!

Is there a parser snap that is converting the binary documents?

My apologies for lack of detail, yes there is indeed a CSV parser following the multi file reader.