This article explains how a group admin can copy a post from one channel to another.  

1. Find the post you want to copy.
2. Tap the 3-dots menu and choose Move.
   
3. On the next screen, add a check mark on the Duplicate checkbox. By default, this is unchecked.
   
4. In the search bar, type the name of the channel where you want the post copied into. In the example below, the name of the channel is Midwest Reports.
5. When the correct channel appears, add a checkmark to choose the channel.
   
6. Tap the Move Here button.
7. You will briefly see the message "Moving...". When this disappears, the post has been copied.