Did you buy it new? If so(according to the Garmin website) it comes with a PC cable.
http://www.garmin.com/products/gps5/
If it didn't then you'll need the Garmin PC Serial Cable for the GPS V.
Don't know if this will work with the V or not, but with my GPS 12 all I have to do is use the Axim Serial Cable, null modem adapter, gender changer, and Garmin PC Serial cable.
(Looks like the same cable, so I'd guess it would.)
There is a place that is selling cables for an Axim/GPS connection. Can't remember the name, but just read some of the threads about connecting the Axim & GPS.