I'm looking at moving my dhcp provider from a Ubuntu server to PFSense.
dhcpd.conf defines my reserved ip addresses.
Where is the equivalent file on PFSense?
There is no file like that which can be edited directly. You'd place the static mappings in the GUI (Services > DHCP Server, LAN/Interface, static mappings section)
If you have a lot of them it may be possible to script a conversion from the existing format to the format in our config.xml, but currently there are no such utilities available.