Hi Mohit,
you need to do 2 steps..
1. check whether data is numeric?
2. Use if without else and pass your source field.
use one udf IsNumeric to do checking
Here we have to use Double class because Integer class maximum support until "1234567891" which around 10 characters only, while you have 16 characters.
Hope your query will be resolved..!! without changing the type in the source and target structure.
Check if this works and share the results..!!
Regards,
Suchita Tomar