well, guitars go up in semitones (a, a#, b, c, c#, d, d#, e, f, f#, g, g#). Their string go from lowest to highest E A D G B E. From that you can work out what note is being played. You can then use the reverse process to stick it on to dulcimer tab
It'll take some work, but you'll need to figure out what notes are being represented by the guitar tab, and then you should be able to play it, unless you dont really know the location of the notes on the dulcimer, in which case the retabbing into a dulcimer tab will most definitely help you learn/memorize where everything is. It won't be quick, though.
would it be easier if i just learned to read actual music? then got the music for the guitar.. and wrote tab under it for the dulcimer? cause.. the real music would look the same, right?