qgis - Visualizing a LiDAR point cloud in 3D with GRASS?

I'm new with QGIS and GRASS so I'm sorry if there is a straightforward answer for this question but I can't seem to get it done.

I've imported a point cloud into QGIS from a datafile. Now I'd like to plot these data points into 3D by using GRASS.

First of all, I couldn't import the QGIS file into GRASS. What is the type of file I need to save the point cloud in QGIS, in order for it to be imported into GRASS?

Second, is it possible in GRASS to add multiple layers in order to create a 3D point cloud?

I really tried everything but the way I'm doing it doesn't quite seem to work.