Inky defaults to conversation mode, but has additional sorting features so you can tailor your messages the way you wish to best see them for you.  To change the filter from the "conversation" view, select the "up/down" icon filter option at the top of the mailbox you wish to change:


Select the "up/down" icon:


That will pop a window with more options for how you wish to see your messages- in this case, move the button from "conversation" to "messages":