This reallly is a "How long is a piece of string" type question. For example if you prefer rice and pasta to potatoes then the numbers vary significantly.
You can also store a ship completely with dried food and reconstitute with water - this is what the round the world people do to cut weight.
The only way to do this is to keep a record of what you eat for a week and size and weigh it, divide your space and intended storage and come up with an approximate figure.
Some people will even store boxes of cans as a false floor in the saloon and work their way through them.
Do you have fridge and or freezer.
Do you make water
do you have the space/inclination to supplement your fresh greens by growing bean sprouts.
I know one crew who measure their journey capability against how long their supply of fresh mint will last before their ability to make mohitos ends!
