Steps to be followed in order to migrate the code
TDLByte #11
Step 1
Load Default TDL Code of Base Release
Base Release: Tally.ERP 9 Release up to which the customization is compatible with. For example let us consider release 4.8 as base release.
  On your Tally.Developer 9 Release 5.0, go to
Tools Preferences Compiler/Execution Options
Select the Tally.ERP 9 32 bit exe for which
the customization project was created
Check the highlighted option