How can I change the number of vertices in surface mesh? I created a surface mesh in itksnap with stl format. I can import it to blender. Please consider it with 3000 vertices and 1700 facets.  At now I want to change the number of vertices to 2200. How can I do it?

Shahrokh
Reduce the number of vertices with the decimate modifier

Add a decimate modifier to the object and set it to collapse.
In the ratio field, enter desired amount / current amount.
If needed, apply the modifier.