I think you need to re-develop in IICS. REST api need to have a platform which transform data and present data.
As Srini mentioned there is currently no API to create a mapping, you will need to re-create.
Now an option you do have is to create mapping tasks. If the talend flows are similar you can create a single mapping that has parameters in the needed places and then use the API to create mapping tasks each time changing the parameter values. The mapping tasks are the runtime executables which gives you some flexability.
if you want to build a re-usable transformation logic, then Mapplet is a solution.
As others mentioned above there is no api to create mapping but there is a api to create mapping task.
Currently the conversion is not available from Talend to IICS, hence you need to rebuild the logic.
You can refer the below connectors available and the mapping task and synchronization task overview.
For complex logics
With lookup and expression for minimal logic
If its incremental/full load
Transformations for logic implementations :