To find out a merge chain for a particular item, follow these simple steps

1. On the merge board, tap the item once to select it - be careful not to tap it twice in case you have a daily objective
2. Tap the information icon (represented by a blue 'i') to the left of the item description at the bottom of the screen.
3. You will now be shown the merge chain required which the item belongs to.
4. You can tap the Where to find? button to find out which Producer you'll need to tap the begin producing the relevant merge chain