Unwrap them and expose to cool, dry air. That should get rid of any surface mould. If the bulbs themselves are soft they are goners.

I have used sulpher dust for mold.

If these were harvested during previous summer, then they are dead.

We don't know if they are dead or not. If they were purchased in the Netherlands they will have been kept in optimal storage conditions up until the time they were put on sale. It rather depends how long they have been in transit and what the conditions were. If they are still firm beneath the mould they could be alive. Then they either need to be planted asap or stored cool and dry until Fall.

Thanks everyone!