If you want:
- "i want that the values entered by the user must be populated in a SQL table
want "the values entered by the user"
then you shouldn't have made
- "a custom list which i modified it and made it as an info path form and on submit"
which I understand as Infopath form was made by pressing a violet button "Modify Form" on ribbon.
In this case the "the values entered by the user" are already persisted by Infopath form of type/compatibility "Sharepoint List Form" through auto-created and locked as non-modifiable during Infopath form creation Main Data Connection (of type Main Data Source) onto a sharepoint list.
The sharepoint list data is stored by Sharepoint server into SQL Server Content database for you automatically by design. And this is unrelated to Infopath
Any reason why do you want to persist data redundantly both into a sharepoint list and into a custom SQL Server database?
I also wrote initially...
Either it is possible through Sharepoint what is most probably not your intention when you asked about submit from Infopath form. From Infopath you should not do it through Sharepoint List Form...
While it is possible to do from Infoapth, you should have asked WHAT you want to do but not HOW (eventually you can not).