Don't search by "Address"... That is Bitcoin Core interpreting the hex value stored in the wallet as a Bitcoin address which will be different to the address shown on another network. Instead, search by TransactionID as that doesn't change across the networks.

In Bitcoin Core, goto the "Transactions" tab, right click one of the transactions and select "Copy Transaction ID". Then copy/paste that into block explorers for the most common altcoins (ie. Litecoin, Dogecoin etc)

https://live.blockcypher.com/ltc/
https://live.blockcypher.com/doge/