As you have confirmed that the file format is (per my comment) as described in the link Re: .dat file from Veris Machine How to Read
There are five columns of data logged by a Veris machine:
Column A: Longitude
Column B: Latitude
Column C: Shallow EC
Column D: Deep EC
Column E: Elevation
You should as per that post be able to import the .dat file into Excel add the appropriate column headings and export as CSV.
You say you need a shapefile to import into the Ag leader SMS database, but the Ag Leader support documentation tells us that CSV file format is supported, so you should be able to import the CSV directly.