I will provide them.

In the key of D, the three main chords are D, G and A7. The chords that will usually be found with them are called their relative minors, because they are related. (We don't need to go into why just now. It's one of those 'just do it and we can get technical later' things.)elative moinor called

D has a relative minor called a Bm.
G has a relative minor called an Em.
A has a relative minor called an F#m.

Some people avoid the 7th--I'm one of them--just because I don't usually like the sound of it. YMMV and you go right ahead and use it if you like it. Most music and guitar backup is a matter of taste. If it sounds good to you, do it :-)

There are a few online places to see what the chords look like. Here's one of them.

http://www.chordie.com/chords.php

You may encounter many chords there that at present have no pertinence to what you want to play. That's ok. Don't worry about it. Some will sound wretched first time you play 'em. That's ok too. They may need other chords to provide the musical setting for the sound it makes. Start with fairly basic chords and don't worry about making mistakes.