Can I display the picture on a wireless screen?

I have a projector that is capable to act as a wireless screen.
It supports Miracast and DLNA is wireless input protocols.

Is there a way to cast the screen from OSMC running on Raspberry Pi 3 to this projector?

Make sure Kodi has UPnP/DLNA enabled. System/Settings, services, UPnp/DLNA, share my libary and look for UPnP players

When you are about to play a file, chose context menus (right click with mouse or c on the keyboard) and Play Using… it will list dlna/upnp renderers.

Remember that your Projector might be limited to which formats it can play.

OK, thank you.

And is there any way to do Miracast?

Miracast has to be implemented by the SoC vendor. The only OSMC device that does this is the Vero 2

All clear.

Thank you very much for answering my questions.