There are two ways through which you can convert SAPSCRIPT into SMARTFORMS as follows:
1. Function module, FB_MIGRATE_FORM.
You can start this function module via SE37, or create a small ABAP which migrates all SAPscript forms automatically.
2. You can also do this one-by-one in transaction SMARTFORMS, under
Utilities -> Migrate SAPscript form.
When converting SAPSCRIPT into SMARTFORMS, only the layout is passed. The logic is still required to be done in the SMARTFORMS.