i need help regarding walet ..

my coin is not showing after sync

but wallet adress showing the balance in blokchain explorer
Try to dump the privkey with the 'dumpprivkey "pubkey"' command. If you own the privkey, you own the asset.
currently iam trying . to resync wallet again but its take so long time

Dumping the privkey has nothing to do with syncing. Best you cut the network the wallet calms down, then you use the command to try to export the privkey.
then how to use that pvt key actually iam new to qt wallet
If you own the private key, you own the asset, independent of any working wallet. Thats's most important.
Have you been possible to export the private key?