@vinaym the first shard has 50 GB , the second one about 40 GB , the third one about 30 GB .. I tried to import shards to culster but he just add 1 and refuse others because the same database name .. i don't know how to till him they are use the same database .. it's just a 1 database .. wierdtrigger engine .. mongo v 2.4

WiredTiger is not with 2.4 version, it works from 3.0 verison. Make sure all mongos, mongo configservers and shards are of same version. Steps to recover is:

1. Backup mongodump all the data on all 3 shards.
2. Drop the databases on all 3 shards.(Instead can start mongo with new datadir, So you dont have to drop database, you still have data safe )
3. Add the 3 shards to the cluster now(there should be no error as its empty).
4. Then Restore the mongodump's taken from 3 shards one by one.
5. This will recover all your data.

NOTE: You can test this in some staging setup with less data and verify steps.

@vinaym Thanks , actually that's what i did and I restored the data from 3 shards ,, but unfortunately I missed about 100 Million document from one collection only. don't know why dumping didn't bring them .. any idea about this ?