I have created an admin grid and also created an associated form for that grid. And then I have created a table for that grid. Now, how to save the form data that particular grid DB table
You have to make a model corresponding to the table, from which you will be able to do all db related stuff.
Following is a good tutorial on how to make model ; https://www.mageplaza.com/magento-2-module-development/how-to-create-crud-model-magento-2.html