POE Switch for IP Camera with Synology?

I want to add IP cameras to my older Synology DS1511+. I am confused about where the POE switch should go in the wired setup.
My system background:
Modem to Router
Router to unmanaged switch to other devices like Apple TV, etc...
Router to Synology
Where in the lineup is the best location for POE switch?
Directly to Router?
Directly to Unmanaged Switch?
Directly to the second port on the back of Synology NAS?

You can connect it anywhere you want. It is just switch. Your router deals with DHCP.