So, we could not find them. What we did was open our Rocket.Chat in Firefox. It will open the custom emoji as a background image/gif. Saved the image/gif and uploaded it to our new rocket.chat. Took a while to get them all but we had the time. 
So, we could not find them. What we did was open our Rocket.Chat in Firefox. It will open the custom emoji as a background image/gif. Saved the image/gif and uploaded it to our new rocket.chat. Took a while to get them all but we had the time.