Isolation of cis-3-hexanol from grass
First, how much compound do you want to make?
Second, how much cis-3-hexanol is there in grass? It is probably around 0.01%, so be ready to process a lot of grass.
Third, it might be reactive (that is it can decompose).  

Your best bet is to:
(1) Figure out theoretical yield
(2) Do steam distillation rather than extraction (bp is 156.5 °C - good for distillation).
(3) Extract collected fraction (mostly water+ some organics including hexenol) with some light organic solvent (hexane, ether). You can try ethyl acetate (aka MEK substitute, bp = 77C), but that is the highest bp you want to go for.
(4) Split organic solution in several fractions and try washing it with water solutions of 5% baking soda and then brine (saturated solution of NaCl). Hexenol should stay in organic solvent unless it decomposes.
(5) Concentrate it under reduced pressure. If you don't have access to rotavap - let it sit in open air. You can direct fan at it if you will, but you might catch fire if you are not accurate.   

You will get a drop of something that is a mix of 20 compounds. How you need to do column chromatography, which is pain even with equipment.  

It doesn't sound like you have access to chemistry lab. In this case for practice purposes try extracting eugenol from cloves first. Grind cloves, place in distillation apparatus, add water, distill. Oil on top is eugenol.  



Steam distillation: Shred grass, add to a gallon of water and distill it off using a lab distillary apparatus.