I moved to Xmonad, which is a great tiling desktop manager.
Usually I launch many workspaces with Xmonad.
I often have some troubles to switch the workspace I would like to use.
please let me know how to show the workspace ID/number on Xmonad.
Xmonad itself doesn't provide any visual indication of the workspaces. However, it provides information about the workspaces which can be displayed by using the statusbars xmobar or dzen. The module DynamicLog offers some possibilities how this information is formatted.
If you don't know about yet, check out the xmonad contribs, which implement many cool layouts and functionality plain xmonad doesn't provide - the DynamicLog module is one of them.