Dense Clouds can have more than 1000 molecules per cm^3
I actually had to laugh when I calculated that.
Cause on the distance you mentioned.
A Dense Cloud capable of Producing Stars would block just as much light as The upper Atmosphere of Jupiter.
Meaning that at this range you would likely not see a Stellar Body which is not emitting light.
Dont forget Dense Clouds are effectively the mass out of which the Stars form.
So they are by far not as *thin* as you seem to think they are.
Http://www.astrobiologia.pl/eana/intclouds.html
http://www.astro.princeton.edu/~dns/teachersguide/ScDensAct.html
1,000 molecules per cubic centimetre isn't especially dense is it?
I'm no expert but for comparison a cubic centimetre of air contains about 19,000,000,000,000,000,000 molecules.