Salome 9.15: creating a 3D mesh from off format file

Hi,
I have an 2D off format file for a geometry.
I would like to create a 3D mesh from this geometry.

When importing the off into SMESH module, I don’t recover any labels on the 2D mesh. Is this normal?

What shall I do to create a 3D mesh?
Note that the 3D mesh shall contain several domains. The interfaces are “meshed” within the off file.

Which 3D algo do you recommend?

Thanks for your help
Best
C