On Guarda, all of your wallets are strictly your own. Therefore, there are no Extra IDs (memos, messages, destination tags) that are attached to your wallets. You can feel free to send funds to Guarda XLM, XRP, XMR, and EOS addresses without specifying any Extra ID.

That said, some services, such as certain exchanges, may enforce entering an Extra ID while withdrawing your funds. In this case, you can specify any random string of numbers and/or letters - it will be delivered to your Guarda wallet all the same.