I did a search on your problem....
Both of the tips beelow come from
Eliminating Mothball Odors
"This isn't an inexpensive solution, unfortunately, but it should work. From a hardware store or home center, you need to purchase some type of "biological" odor killer or odor eater. Odors Away is one. I think Odors Begone might be another. Something of that nature, but the words "biological" must be in the description somewhere.
This is expensive stuff, but it works! They're odorless; you can use them on your skin, your pets, in your house, all over. They remove cigarette smoke, skunk odors, septic odors - you name it! Great stuff. Save up your pennies and try some. You should just be able to spray the clothes and air them out or you might even pour some solution into the wash when you try again. It might take several applications to remove the entire odor, but it will work!"
and
"Take a large trash bag and put your clothes in it along with dryer sheets (like Bounce). Let them sit for 48 hours (or longer if needed). Your clothes will smell great! I used this method when I took my belongings out of storage after 3 years!I washed the sheets, pillowcases, curtains and clothes but still had moldy or mothball smells. They disappeared when I put them in trash bags with the dryer sheets. It seems to absorb and remove the odors."