what to dowith 100green plums

Not sure as they aren't ripe yet and i know that they wouldn't be very pleasant to eat, sour and hard before they turn purple...

Oh dear... well you could try making chutney with a small number of them and see if it is edible.

What a shame...hang the branches up somewhere dry and warm - in a garage perhaps and maybe some will ripen up - although very doubtful.
I know there are a number of Persian dishes that use unripe plums - not sure quite how unripe of course! Anyway - I looked on dear old Google and found one site called Chowhound and it offered this suggestion....

Out of some of them you could try making green Georgian sour plum sauce which is very good with grilled meats and roast chicken apparently.

For ~2 lbs unripe (sour) plums: simmer with water to cover until soft, about 10 mins (time varies w/size of plums). Drain, pit and put through strainer or food mill, and return puree to saucepan. Mix in 1 tsp chopped garlic, 1/4 cup each chopped fresh coriander and dill, 1/8 tsp hot paprika and ~2 Tbsp lemon juice (more or less to taste, depends on how tart plums are). Salt to taste, bring to boil and simmer 2 minutes; cool and store in bottles in fridge.

Best of luck!