A transaction is confirmed when it is included in a block, so you will need to watch for a message that alerts your node (or whatever software you are using to watch the P2P gossip traffic) to a new block, that includes the transaction in question. It doesn't matter if a node run by a miner relays your transaction to other nodes on the network, it only matters that the transaction is included in a block that is included in the longest (most work) valid chain.

Note that the relaying of this information has been optimized through various BIPs, so that the network is not naïvely using more bandwidth than required. This means that a message explicitly listing your transaction as confirmed may never be encountered, instead a node can gain this information implicitly, through the use of their mempool, and computational filters included with the new block message. You should take some time to learn about these optimizations if you're working to understand the network's P2P traffic, there are some questions on here that have more info. This one may be a good starting point.