This is a good tutorial on how to convert points shapefile to contour lines:
The summaries of the video as follows:
A: Points to Spatial Area (Contour)
- Using Topo to Raster plugin: ArxToolbox > Spatial Analyst Tools > Interpolation > Topo to Raster
- Then, select Input feature data > field (the z-value that we want) > Type > PointElevation
Points to Spatial Area
B: Contour to Contour Line
- Using Contour plugin: ArxToolbox > Spatial Analyst Tools > Surface > Contour
- Then, select Input Raster (tiff. from step A.) > Contour Interval (distance between two lines. if the interval between line is 20mm, select 20. It is not the no. of contour interval)