I do not know, but maybe the information in this article could help you: Article Converting simulated total dry matter to fresh marketable yi...

Or maybe you can simply use: Fresh yield=(dried yield/%of dry matter of the fresh onion or cabbage). Acording to https://ndb.nal.usda.gov/ndb/foods/show/2888?manu=&fgcd=&ds= , the raw onion contain 10.89%, and cabbage 7.82% of solids.

I hope that helps you.

you can use this conversion

Dry wt= calculated moisture value of the sample x (100/100-%moisture)

Agree with Dr. Melese Temesgen

% moisture content in wet basis = 100 x (% moisture content in dry basis/(100+% moisture content in dry basis))

also if your known % moisture content in wet basis(weight of water in material/total weight of wet material x 100) your can convert % moisture content from wet basis to dry basis by this formular

% moisture content in dry basis = 100 x (% moisture wet basis/(100-%moisture wet basis))

1. you can convert total dry weight to fresh weight of onion assume you known % moisture content of onion in dry basis

so fresh weight of onion = total dry weight of onion x ( % moisture content in dry basis/100) + total dry weight of onion

= total dry weight of onion x (% moisture content dry basis +100)/100

2. you can convert total dry weight to fresh weight of onion assume you known % moisture content of onion in wet basis

so fresh weight of onion = total dry weight of onion x (100/(100-% moisture content in wet basis))

Agreed with Tansong Chayawattana method.