Hi Ayush,
Is your 2.1 system on .NET or NW?
Which type of implementation are you using - Live or Staged?
The reason for re-implement is that the applications changed significantly at 3.0 (and at some points during the product since then to its current version).
So simply importing your build will not work. In fact, in v2.1 there was no concept of configuration build exporting nor the .delta file structure used to support this process.
Obviously you have your existing config and if you have your existing requirements documented then this can help speed up any re-implementation effort.
Stephen