You can buy Xenon Turbo here. It's a monthly subscription that can be canceled at any point. The price might change in the future.
Xenon Turbo can save and load up to 250 messages per channel. Just the
x:backup create 250 to take advantage of it.
If you want to copy even more messages, you can use the
x:copy messages command. It can copy up to 1000 messages from one channel to another.
Xenon Turbo is able to save and load emojis. Just add the
emojis option to the
options parameter of the load command. Keep in mind that it can take multiple hours to load all emojis, due to discord rate limits.
You can also use the
x:copy emojis command to directly copy all emojis from one server to another.