See for instance: Implementation — FEniCSx tutorial for how to evaluate at one (or several points in your domain).
When working with a vector function space (assuming a non-mixed function space), the dofs are blocked as (dof_x(p_0), dof_y(p_0), dof_z(p_0), dof_x(p_1), dof_y(p_1), ...dof_z(p_n)
where these relate to the coordinates of the function space (not necessarily the mesh) by p_i (point i) is V.tabulate_dof_coordinates()[i,:]
If you really want to map mesh nodes to dofs, see: Application of point forces, mapping vertex indices to corresponding DOFs - #2 by dokken