I assume it was a typo, with the correct units being ml.
A handy web page for volume unit conversions (if you don't have a calculator handy) is: http://www.ilpi.com/.../volumeunits.html They have similar pages for mass, etc.
30 microliters is 0.0010144 ounces, so 30 nl is 0.0000010144 ounces.
Supposedly 24 drops = 1/4 teaspoon, and 1 teaspoon = 0.1666667 ounces. The conversion from nl to drops is left as an exercise for the reader.
Cheers,
Scott.
(Who feels like dissecting the frog this morning.)