get almost good scanns but how to do next

When you have it meshlab, you will see it has both a point cloud and a mesh.  ON the Top tool bar, click the points only view (next to the cube icon).  This will show you the point cloud only, similr to what you see in the preview.

For the top menu, select Filters/Sampling/Poison-Disk Sampling.  In the pop-up menu, number of samples input a number that is close the umber of vertices.  If your scan is particularly noisy, reduce that number.  The higher the number, the longer it will take to process the filter.

When it's done, a new point cloud will be generated.  Click the layers button in the tool bar (it looks like stacked sheets).  On the right you will see the layers, and you can turn them on and off, and select which layer to work with.

Next click the newly created mesh, from the top menu select Filters/Remeshing-Reconstruction/Surfcase reconstruction: poisson.  In the pop-up  input 10-12 in the Octree depth, and 7-8 in the solver divide.  Click apply, and wait for the mesh.  It will generate a new mesh, which you can then clean up.

If you want, to, you can also skip the middle steps and go directly to the Surface reconstruction.

good luck