If you have sent a transaction from your MyMonero wallet to another wallet, and if the funds have successfully left your wallet but have not reached the destination wallet, please contact the recipient wallet service to query the missing funds.

If the transaction is coming into your MyMonero wallet, you will need to first confirm that the correct address was used when completing the transaction. 

All Monero transactions require a minimum of 10 confirmations before it can be considered completed.

These 10 confirmations are on the blockchain, and once completed, the transaction is permanently saved on the blockchain.

The time frame that it takes for these confirmations differs from transaction to transaction, but on average it should not take much longer than 30 minutes.

But it can sometimes take slightly longer, this should not be a concern to you.