Can I use the autoland if I have to land on an airport which is not known to my FMC database? Is it possible to insert the coordinates to get the autoland mode?
Autoland is an autopilot mode. AUTOLAND could be « armed » while the autopilot is receiving FMS inputs, but once it is « active » it doesn’t use FMS data but the ILS receivers or the ILS and GPS receivers.
No need of the FMS neither for the approach, nor for AUTOLAND
Right now the only technology to perform a full autoland relies on ILS (and in increasingly rare cases MLS), and then only when the airport and plane allow CAT III operations. Since ILS relies only on radio navigation based at the airport, no GPS coordinates are required. ILS approaches are quite handy if for some reason you are working with an unfamiliar or unreliable GPS or FMS.
However, there are several practical reasons why autoland at an airport that's not in the FMC might be more difficult, besides being highly unusual. If you're used to LNAV and VNAV, those obviously won't guide you to the approach. Similarly, not having RNAV or LPV available can be inconvenient if the airport isn't using low-visibility procedures for ILS CAT III and you have to land using some other procedure. Finally, CAT III landings have a number of disadvantages listed here like increased pilot workload and higher operational requirements.