There are several ways to do this, but here is one easy (sort of) way that several people have used:
1) First, you will need to download an application called BMGPX from http://parkrrrr.com/. This is a DOS application that will convert the benchmark file into a GPX file that we can use on the PDA.
2) Next, you will need to obtain an "official" .DAT file from the NGS. Go to their web site at http://www.ngs.noaa.gov/cgi-bin/ds_county.prl and click on "Archived Datasheets", then click on "Yearly_Archives". Highlight "Arkansas" and click "Get County Archives". Choose the county you want and and whether you want it zipped or not, then click "Download File". You will get a .dat file that you can now use with BMGPX.
3) Make a new directory on your computer and put both the BMGPX.EXE and the county .DAT file in there. Go to a DOS Command Prompt and navigate to that directory. Now type:
bmgpx xxxxx.dat yyyyy.gpx
xxxxx.dat is the name of the .dat file that you just downloaded and yyyyy.gpx is the name that you want to give the GPX file. Hit ENTER and VIOLA!!! you have a GPX file containing that county's benchmarks that you can use in Watcher, GPXSonar, Cachemate, etc. on your PDA!