OK, so I'm in the process of sending my coins to a newly created address in the new wallet. Is there a command to check if the address is in the wallet, to be 150% sure that I won't be sending the money to an address I don't own?
listaddressgroupings outputs nothing
The only thing to check if you properly the right address is to double check or more the address you will gonna send the BTC. You can check on the blockchain website the pending transaction on your new address once you successfully transfer funds.