Hunebedden 38-47 are all accessible from Emmen.
Of particular note is D43 Schimmeres, a long grave with two hunebedden within it. It is just 15 minutes walk from Emmen bus station.
You can easily visit them all on foot in a single day. The two farthest from the bus station require a 45 minute walk each way, so taking the No 2 bus will be helpful.

You can find details of how to reach all the hunebedden at
http://www.themodernantiquarian.com/site/9820/netherlands.html