Kate, a lot of people have been playing dulcimer for many years and have no idea what notes they are playing. That's part of the beauty of the instrument: you can play it even with no understanding of basic music theory.
But of course, any little knowledge you gain will help.
Chords are indicated with three numbers. The first number refers to the fret you play on the bass string, the second number refers to the fret you play on the middle string, and the third number refers to the fret you play on the melody string. So 0-0-2 is a D chord played with the bass and middle strings open (unfretted) and the melody string fretted at the second fret.
However, two things make chording even easier than that on the dulcimer.
First, if you are tuned DAd, all your chords are reversible. So, for example, D can be not only 0-0-2 but also 2-0-0 and Bm can be 0-1-2 or 2-1-0.
Second, because we only have three strings, we cannot play complicated chords. A seventh chord technically has four notes, but we can only play three of them. And we use that principle for three-note chords, too. So often we play two notes of a chord rather than all three. So most of the time beginners will play 1-0-1 for A or A7 even though only two notes are being played.
The chord chart I link to above shows you various places around the fingerboard to play all the chords you need for this song. But if you are a beginner, I suggest playing the easiest versions down near the nut, making use of as many open strings as you can.
For D: 0-0-2
For A: 1-0-1
For Bm: 2-1-0
For G: 3-1-0
For E: 1-1-1
For A7: 1-0-3
And I know you feel alone right now, but you are in a part of the country where there actually are dulcimer players. The festival season is basically over, but keep your eyes open and you'll notice dulcimer festivals around where you can join workshops and just watch other players. There might even be a dulcimer group nearby that you can join. When I first discovered the dulcimer I played for about a year before I heard another dulcimer live other than my own. But about two years ago I started a local dulcimer group, I now have dozens of people on my mailing list, and we've been meeting monthly since then! I'm sure you'll be able to find some folks nearby as well.