If you only have one record per file then this is a simple read loop.

    #!/bin/bash
    
    read_data()
    {
      local first last addr city state zip
    
      while read -r header data
      do
        case $header in
          FirstName:) first=$data ;;
           LastName:) last=$data ;;
            Address:) addr=$data ;;
               City:) city=$data ;;
              State:) state=$data ;;
                Zip:) zip=$data ;;
                   *) echo Ignoring bad line $header $data >&2
        esac
      done
      echo "$first,$last,$addr,$city,$state,$zip"
    }
    
    for file in *srcfiles*
    do
      read_data < $file
    done

The `read_data` function reads each line and splits up the line into a "header" and a "data".  Once we get to the end of the file we just print out the results.

We call that function once for each source file via the `for` loop.

Note some potential gotcha's:  If there are commas in the data then this will break things, so you might want to do

      echo "\"$first\",\"$last\",\"$addr\",\"$city\",\"$state\",\"$zip\""

as the output to enclose everything inside `"..."` layout.  If there's any `"` in the data then this may cause the CSV to be malformed as well.

Adjust the `echo` line to match the format you want.